Start with the repository README if you have never used phyphox. Then:

page	what it answers
Getting started	install, first sketch, per-board notes
Concepts	what the phone receives, channels, polling, memory, strings, errors
Views and graphs	`View`, `Graph`, `Value`, `InfoField`, `Separator`
User input	`Edit`, `Slider`, `Dropdown`, `Toggle`, `Button` and the board-side callbacks
Phone sensors	reading the phone's sensors on the board
Export	what the app's export button produces
API reference	every class and method on one page
Protocol	the BLE services and characteristics, the experiment transfer

For existing projects: Migrating from 1.x and the Changelog. For contributors: Testing.

These pages are also published as a website, together with the reference of every class and method generated from the headers: https://phyphox.github.io/phyphox-arduino/.

The phyphox file format itself — what the generated experiment means — is documented in the phyphox documentation (the "file format" section), which is the canonical reference; this library only generates a small subset of it. Version 2.0 declares format 1.20.