How do you understand a large chunk of code?

Question

I am a fresh college grad student that just started my job. In my ramp up period, I need to learn a lot of product code. There are some design docs but they do not help much.

Answer 1

This is obviously a pretty common question, and it's similar to this one (and the questions related to it): How to understand the design and code flow of any product quickly?

Dig through some of those answers / comments, for starters. Else, we'll just end up repeating them. :)