Which tool to choose
They're not equivalent. Choose based on how you learn.
If you want a clear, clean explanation, right away → free ChatGPT. The free tier today runs on a current-generation model, no longer a year-old fallback version: for people who don't pay, this changes quite a lot of what you can get. On top of that, it has a built-in study mode (more on that below).
If you learn by looking (diagrams, images, videos) → free Gemini. It automatically inserts images, diagrams, and YouTube videos into its answers, to help you with complex topics. It's the right choice if "seeing" helps you more than "reading."
If you need to have a long document explained to you (a contract, a set of lecture notes, a 40-page PDF) → free Claude. It has a very large context window: in practice, it can keep a document of hundreds of pages in memory and discuss it in full, without losing the thread halfway through.
For the basic need — "explain this thing to me in simple words" — any of the three works. Start with the one you already have open.
How to do it
The secret isn't the tool: it's telling the AI who the explanation is for and at what level you want it. Without this, it answers you like a university textbook.
- Open the AI you've chosen (the path doesn't change whether you're in a browser or an app).
- Don't just write "explain photosynthesis." Write who you are and what you need.
- Paste a prompt like this:
Explain [the concept you don't understand] to me as if I had never heard of it.
Constraints:
- use everyday words, no technical jargon
- if you have to use a technical term, put it in parentheses with the explanation right after
- start from a concrete everyday-life example, then arrive at the definition
- maximum 150 words
At the end, ask me a single question to check whether I really understood.
- Read the answer. If a point remains unclear, don't start over from scratch: write "The point about [X] isn't clear to me, rephrase it with a different analogy."
- Answer the question the AI asked you. That's where you find out whether you grasped it or are just nodding along.
Check: if after step 4 you can explain the concept out loud to a friend in two sentences, it worked. If you're still clinging to the AI's words without understanding them, ask for a different analogy: often it's just the wrong metaphor for you.
Study mode: when you want to understand, not just know
If your goal is to learn (an exam, a skill), there's one more weapon. ChatGPT has "Study and Learn" mode, Gemini has "Guided Learning," Claude has "Learning Mode": instead of handing you the answer, they guide you through the material. In ChatGPT you'll find it among the chat tools (look for the item dedicated to studying) and it's available even for people who don't pay: the AI becomes Socratic, asking you guiding questions and giving hints instead of spitting out the solution right away.
A concrete example
Marta needs to understand what "compound interest" is before signing a savings plan. On Google she finds only formulas. She opens free ChatGPT and writes:
"Explain compound interest to me as if I were 12, with a real-money example. No formulas. Maximum 120 words. Then ask me a question."
The AI answers with the example of a snowball rolling: 100 euros that produce interest, and the next year the interest produces more interest on top of itself. It closes by asking her: "In your opinion, after 2 years do you earn more with compound interest or with simple interest?"
Marta answers "compound," the AI confirms and adds the why in one line. In four minutes she has understood something the bank's page had never made clear to her — and now she knows which question to ask the advisor.
When it does NOT work (and how to fix it)
If the AI still answers too hard
It means you didn't give a concrete reference point. "Simple" is vague for a machine. Give a measurable yardstick: "explain it to a 10-year-old child," "explain it as if we were at the bar," "use only words I'd use with my grandmother." The more precise the audience, the more the answer drops down to your level.
If the AI makes up details
It happens: models sometimes produce plausible but false information. With web search on, the margin of error drops quite a bit, so keep it on when you ask for facts, dates, or numbers. And for any data you'd use to make a decision (figures, dosages, laws), verify it against an official source. The AI is excellent at explaining, it's not a primary source.
If you change the question three times and it blocks you
Free plans have usage limits. The exact numbers aren't public and change with server load, account age, and message complexity: in practice you chat for a while, then you may get slowed down. Fix: if it blocks you, switch to another tool (free Gemini or Claude) to finish, or wait for the unblock. Often ChatGPT doesn't cut you off entirely: it switches to a lighter model, but you'll notice the quality difference on complex things.
If the concept is inside a document you can't attach
On Claude you upload the file and have it explain the difficult passages: at the free tier you can upload documents and use web search. Attach the PDF and write "explain only section X to me in simple words."
A tip from someone who really uses it
The explanation that clears up your ideas isn't the first one: it's the one that comes after you've answered the check question wrong. When the AI asks you "did you understand X?" and you get it wrong, that's where you discover the real gap. Don't skip that question out of haste. It's the only moment when you stop reading an explanation and start owning it. And a trick that works almost always: ask "explain it to me with an analogy taken from cooking" (or from sports, or from traffic). Metaphors drawn from your everyday world glue concepts into your head far better than correct definitions.
Frequently asked questions
Do I really have to pay to get good explanations?
No. For explaining concepts, the free plans cover you without problems. The idea that the free plan is useless is outdated: today the free tiers have many more features than they used to, and to understand a concept you don't need anything else. You pay only if you bump into the usage limits every day.
What's the simplest prompt if I don't want to write that whole long one?
This sentence already does 90% of the work:
Explain [concept] to me as if I were 12, with an everyday example.
The phrase "as if I were 12" (in English "ELI5," Explain Like I'm 5) forces the AI to drop the jargon.
Can I trust the explanation or do I have to check?
Trust the logical structure (how a thing works, why), verify the specific facts (numbers, dates, names). For facts, keep web search on and cross-check with an official source.
But if I use AI to understand, am I not actually learning on my own?
It's the serious objection, and it's the reason study modes exist. Instead of handing you the answer, they slow you down and guide you through the process step by step: the AI stops being an "answer machine" and becomes a "study companion." The risk isn't the tool, it's pasting and copying without reasoning. If you answer the check questions and try to rephrase in your own words, you learn more, not less — because you have a patient tutor who adapts to your pace instead of a textbook that moves at a single speed.