Circuit Python
Circuit Python is a dialect of the Python programming language targetting microcontrollers. It is maintained by Adafruit.
The programming experience with Circuit Python is based on writing and copying Python source files to the device through your computer's file system. This means you can write Circuit Python code in any text editor. With that said, there is an ecosystem of recommended tools that make the process even easier.
Documentation for the Circuit Python language and core libraries are available at https://docs.circuitpython.org/.
Adafruit provides excellent, beginner-focussed documentation on how to use Circuit Python at https://learn.adafruit.com/welcome-to-circuitpython.