The Debug property indicates whether the operating system is a checked (debug) build. Checked builds provide error checking, ...

The Debug property indicates whether the operating system is a checked (debug) build. Checked builds provide error checking, argument verification, and system debugging code. Additional code in a checked binary generates a kernel debugger error message and breaks into the debugger. This helps  immediately determine the cause and location of the error. Performance suffers in the checked build due to the additional code that is executed.
Values: TRUE or FALSE, A value of TRUE indicates the debugging version of User.exe is installed.