You'll get familiar soon enough, honest. Meanwhile, just ask. And I'll tackle those.
There are 3 basic types of feed, starter, grower, layer. Starter up to maybe 8 or 10 weeks, grower til point of lay around 20-25 weeks, then layer. Scratch is a treat / snack, not a complete food; they love it but it is usually much lower in protein than regular feed so it's similar to giving candy to kids, you want to do it in limited quantities. It's more complicated than that, there is also game bird feed and flock raiser, for example. Just to really confuse you, I don't feed anything but grower as I have a mixed age flock, from month old chicks to 4 year old hens. The only biggy caveats besides "scratch isn't a complete food" is "don't give chicks layer til they are laying age." Grit is just small pieces of granite. They use it in place of the teeth they don't have, in their gizzard, which grinds any foods needing grinding. Some buy bags of grit and some depend on the little rocks or rough sand in their soil. A run is a fenced outdoor area usually attached to the coop -- many, many different styles are used -- a quick look at the coop section will show you. The alternative is what is called "free range" here, which again has many meanings, anything from being turned loose onto acres of land, to being turned loose in a fenced suburban back yard.
We often tell our noobies, there are no stupid questions. We all remember when we were noobies, often not that long ago!