For tasks like brainstorming, changing your writing style, or summarizing information, any of the major AI models can be used: for example, ChatGPT, Claude, Copilot, Gemini, Perplexity, or NotebookLM.
Back in 2023, ChatGPT did not have the ability to search the web, so it was mainly useful only for tasks like these, not for looking up facts. Now that all the models have search they can be used for many kinds of tasks.
It's still possible for them to get some facts wrong, but they do this less often than they did before they had search.
When asking for a summary, you might consider a prompt like this:
I will upload a document and I'd like you to summarize this and directly quote the sentences that best illustrate the overall themes. Also identify the most surprising ideas.
This will often produce a better summary than only saying "summarize this." Get more summarization ideas in this article: Best Prompts for Asking a Summary: A Guide to Effective AI Summarization.