Start here, because it decides everything else: Quizlet's help centre says Ask Quizlet "is currently only available for users in the United States who are 14 years old or older." If you're outside the US or under 14, nothing on this page will appear for you, and the honest move is a general chatbot instead — start with our Text & Conversational AI category.
You need a Quizlet account and to be signed in, but you don't need to pay. Quizlet's help page for Ask Quizlet names no subscription requirement and no usage cap. That's worth a pinch of salt rather than a guarantee: Quizlet does cap its other AI features by plan — its study-guide generator is "limited access" on a free account and unlimited on a paid one — so a cap on the chat may exist without being written down. Check for a limit once you're signed in. Paid Quizlet Plus is a yearly subscription (also sold monthly as an in-app purchase on Apple devices), and what it buys is more of the other AI tools, not obviously more chat.
You can type a question, or attach your own material and add a prompt (the message you type) saying what to do with it — Quizlet says up to three files at a time, in .pptx, .docx, .pdf, .png, .jpg or .jpeg, and under 25 MB each if you're on a phone.
The conversation is not kept. Quizlet says plainly: "Chat history isn't saved across pages. If you leave Ask Quizlet, the conversation will reset, but minimizing it will keep your chat active." So if it explains something well, copy it out or turn it into flashcards before you navigate away.