The term "bumping the shoulder" refers to partial full length sizing, this can be accomplished a number of ways, with body dies or FL sizing dies, or a combination of both of these and a neck bushing die.
This sizing technique differs from FL sizing by only bumping the shoulder the minimum amount to allow a fired case to fit the chamber with minimum headspace, that is what the .002" refers to, the head to shoulder length. A FL sizing the traditional way will bring the shoulder back to minimum SAAMI dimensions, which may be .006"-.008" or more from chamber dimension, this sizes the brass too much and can lead to short case life.
A neck die is the other method of sizing, but due to the brass expanding after each shot, it will eventually need to be either FL sized or partial FL sized so it will chamber easily again. The partial FL sizing is the preferred method if you want to extend case life and in most instances, accuracy too.
I suggest you buy yourself a loading manual that sets out the different methods clearly and simply so that you can decide which method suite you best.