I have discovered 2 different sets of documentation for the ESP32. One appears to be maybe closer to the hardware. There are similar api calls, but different names. The links are to the top, drill down to whatever topic interests you and compare. I was interested in timers so that is where I ended up.
I think this is the one we are supposed to use
https://espressif-docs.readthedocs-hosted.com/projects/arduino-esp32/en/latest/index.html
But there is also this
https://docs.espressif.com/projects/esp-idf/en/v4.3/esp32/index.html
Anybody know why two?
First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.