Definition
A reverse engineer starts from what the player exposes: assemblies or native binaries, metadata, asset files, saved data, and network traffic. They decompile or disassemble code, follow it in a debugger, and test what changes when values move. The goal is a working understanding of the logic, enough to change it, copy it, or bypass it.
Relevance
Reverse engineering is how you understand a program when you only have what shipped. For a Unity player that means reading assemblies or the native binary, metadata, assets, and saved data until the behavior is clear enough to explain, reproduce, or change.
Example
A reader opens the metadata, finds a method tied to a daily timer, and follows it in a debugger. The method compares the device clock to a saved timestamp and grants a reward. That is the whole check, recovered without the project.