This is right-alignment.
This is center-alignment.
This is justified, which means it stretches or squishes so that every single line is exactly the same length.
But that isn't actually the kind of alignment we're talking about. I mean, it's part of it, but not all of it.
What alignment means is that all the parts of your document should line up nice and neat. You shouldn't
jump all over the place
and make it
That's what poetry is for.
Alignment is your mom telling you to clean up your room, or your teacher telling you to organize your desk/locker/binder. If your document is a mess, people will just look at it and cringe. They won't want to read it, because they'll have trouble finding their way around. You know how when your room is a pigsty, you trip over everything and can't get to your bed? That's poor document alignment.
I'm not saying you need to line everything up perfectly in cute little grids. I'm not even saying you have to "justify" your text to make pretty little columns like they have in the newspaper. (In fact, I'd prefer if you didn't. It's harder to read that way.) I'm just saying it should be tidy enough that I know what's what. And getting back to repetition, the sub-headings should align with other sub-headings on the page, headings should align with other headings, and so on. See? They tie together so nicely.