ERP Associates, Inc.

Hello,
I have a doubt while comparing a project between two databases . I am providing the details here please if someone could help me.
As I read the peoplebooks on this topic, they say that when we compare a record or field in a project between source and target, the project gets repopulated with the difference in the records . Does that mean the source project gets changed ?
I think this should not be the case that just by comparing source filed or records would get changed itself.

Or is there a upgrade project generated with the difference between the databases which is another entity rather source records and that ensures my source has not got changed?
I am in a dilemma since two days. Please see if someone could answer the question?