From the top of the webpage, "CircuitPython is a programming language designed to simplify experimenting and learning to code on low-cost microcontroller boards

From the top of the webpage, "CircuitPython is a programming language designed to simplify experimenting and learning to code on low-cost microcontroller boards." It targets beginner hobbyists and the lower grade education market. The changes from MicroPython are designed to make getting code on to the board and executing easier for those users. When a microcontroller board with CircuitPython is connected to a computer it appears as a USB drive. To install your code and any supporting files on the board you just drag and drop them on the drive vs having to upload them using something like Thonny with MicroPython. Also when you drop your code on the drive the board automatically resets and begins executing the code. It also has some changes to make code more portable across the different microcontroller boards it supports.