Debug mode and Release mode are different configurations for building your .Net project. Programmers generally use the Debug mode for debugging step by step their .Net project and select the Release mode for the final build of Assembly file (.dll or .exe).

 The Debug mode does not optimize the binary it produces because the relationship between source code and generated instructions is more complex. This allows breakpoints to be set accurately and allows a programmer to step through the code one line at a time. The Debug configuration of your program is compiled with full symbolic debug information which help the debugger figure out where it is in the source code.