SQL creates a log file and records every change in it. However, it is not normally readable by you without third party software. This file will grow to mamouth proportions if not backed up regulary and shrunk. The purpose of the log file is to be able to recover data (and sometimes to a point in time to undo a bad action like accidentally delting the wrong table).
If you want to see who made what changes and when, then you need to set up audit tables and triggers to automatically put the information you want in these tables. I believe there are also 3rd party tools which can help you set this up.