What is the difference between compiling and building in Delphi?

Question

With Delphi-6 there are two options: Build and Compile.

I know when I run a program it compiles only the files which have changed and uses the DCUs for those which h

Answer 1

You should always Build when changing settings.

The previously compiled DCU files may have been compiled with different settings, such as compiler defines. Which can cause two units in the same project to be compiled with different settings.