Complex sentence: One of the most important changes was that DarkBASIC Pro uses true machine level compilation which allows it to be significantly faster than DarkBASIC, which created executables by appending a program's source code to a copy of the interpreter.
Split into simpler sentences: One of the most important changes was that DarkBASIC Pro uses true machine level compilation which allows it to be significantly faster than DarkBASIC. DarkBASIC created executables by appending a program's source code to a copy of the interpreter.