In view of Dealing with answers in comments.?, let me just duplicate a general advise that I've posted earlier in a comment.
Since GAP is an open-source system, one can easily examine the source code to see how it works. In GAP 4.5, new function
?PageSource) was introduced. It will show you the file with the source code, so you will be able to see the comments in the code, too (if there are any). Note that the argument must be a function, so for operations etc. one has to use ApplicableMethod first. Try the following examples from the GAP manual to see what happens:
met := ApplicableMethod(Size,[ct]); PageSource(met);
met := ApplicableMethod(\^, [(1,2),2743527]); PageSource(met);