Multi-part archives are used to break large games into smaller, more manageable download sizes. You generally need all parts (part1, part2, etc.) in the same folder to successfully extract the game.
This file name typically refers to the first segment of a multi-part compressed archive for the PC game . In this context: Team.Sonic.Racing.FULL.UNLOCKED.part1.rar
Usually indicates a version of the game that includes all files and has had digital rights management (DRM) removed or bypassed, allowing it to be played without a standard license or installation from an official store. Multi-part archives are used to break large games