What are the actual differences between the two? I am new to LaTeX and I need to create a custom "look & feel" -- should I be looking into making a class or a style?
To answer your question directly: imho, you should start by seeing if you can tweak one of the ready-made
In each of these classes, you will likely use packages to help you tweak the appearance such as
Once you are familiar with these classes, you can move on to some of the more intricate classes such as
Once you've produced a few simple documents and you want to put some 'bling' into them, you could start by reading the following post, and the answers within:
In modern LaTeX a class is one of the major formats for documents. It is invoked using