User Data (UD) is a data area located outside the user code area (from 0x0FE00000). Programs cannot be placed in this area, but it can be used as a data area. As a use case, it is often used instead of EEPROM to store calibration data, product information, etc.
It is assumed to be written and erased from the user code, but it is also possible to do it from Simplicity Studio, although it takes a little time. Please refer to another topic for the method.