NotebookLM is a personalized AI assistant designed to help users with thinking, summarizing, and brainstorming. Users can create notebooks, add Google Docs, PDFs, or copied text as information sources, and then ask NotebookLM questions to assist with explanation, summarization, and brainstorming. Users can also click on information sources to automatically generate summaries and key themes. NotebookLM's strength lies in its personalized assistance, allowing users to trust the information it provides and build upon it for their work.