Grammar words also sound so lovely. Language-y words sound fabulous too: declensions, conjugations... Delightful!
Commas are to divide off sub-clauses as long as they don't have a linking word such as "and". Best way to think of it is "where would I pause in this sentence?" and that's usually where the comma falls. Although sometimes, to be honest, it's a bit hit and miss. That sentence was deliberate as it had a cool aside which also requires a comma, if you see what I did there. Commas are quite fluid really. Semi-colons are godly and should be used more.