Robert, I'll give you credit, you're really trying to learn the lingo. Here are a few answers to your questions, not all but a few
When you put a freight at a certain place so it can be loaded, unloaded, repaired, you "spot" the car. If you have a siding ahead of you (a "facing point" switch), like coming to a fork in the road, you can't pull the car in or your engine would be blocked in. So you go to a double ended siding, leave the car on one track, and "run around" the car on the other track. NOW you can push that car into the siding to spot it, then go on your way.
When doing a brake test, the brakes must be applied. I will point out there are several different types of brake tests in the government regulations, and each one is done a bit differently. But after the brakes are found to be OK, they must be released. Rolling the release means instead of walking past each car to observe the brakes are released, the crewman or inspector stands in one place while the train rolls past him (or her), watching and listening for any car which did not properly release.
Goat is another name for switch engine. This means the engine being USED to switch cars - not a physical type. You could have a mainline engine and if it's being used to switch and spot cars, it's the goat.
Most locomotive throttles have 8 notches for power, so when a loco is in the 8th notch it's wide open - like flooring it in your car. (Any of those old GE's with 16 notches still around?)
A joint is a coupling or a hitch - that discussion pertains to whether or not it is safe or allowed by rules to be riding on the car or power when it couples on to something else.
And while I'm confident in what I've told you here, remember in the future different places use different terms. In most yards you switch cars, but in the east around the former Reading, CNJ, and a few other lines, you "drill" them. Maybe other places, too. It's part of what makes this stuff interesting, every place is different, you learn new things every day.