What nodes are there in Nodes?

The node menu (N or /) groups them in five sets:

Media: Upload (your base image), Reference (an image with its role: material, furniture, style…) and 3D model.
Text: Text (the prompt), Image scanner, Mood extractor, Style and Assistant.
Generator: Image Generator, Video and List (to run in batches).
Editor: Enhance render, Lighting, Camera angles and Image Upscaler.
Organization: Group and Sticky note.

Each one has its own article in this section or in “Enhance, upscale and edit”. The full reference, with what each node accepts and produces, is in “Nodes & connections”.