Source code is typically commented and much more readable, easy to follow and understand what is going on, for a programmer. Its the code the programmer writes and reads.

Code could be the same but also might be the compiled code, which is stripped of helpful comments and nicely named variables etc, so is much harder to understand even for a programmer. Its the code the computer writes, based on the source code, and reads into its memory to do the calculating and controlling of monitors and whatnot.