What does 'relocation' mean?
Relocation means moving stuff from one place to another. In your case, there is a program which contains some absolute addresses, which make sense if the program is located at a certain address A. If the program is loaded to a different address B, we need to update all of these addresses, translating them by B&minus;A. This is address relocation. A loader (a program loading another program to memory) which does this is called a relocating loader.