Question

Could anyone tell me how to use a gdb debugger for C to analyse code.
By the way what does the phrase 'Stepping through the code" mean?

Answer 1

The question you asked has a huge scope. Read this out: http://c.learncodethehardway.org/book/learn-c-the-hard-waych32.html and then return back here to clarify your doubts.
Stepping through code means running code step by step to find the erroneous branch/loop etc. There are other terms like step into, step over etc.