Prairie's
Pshaw, we all are learning, and I don't guess anyone was born knowing all about 'maters. The beauty of it is, you can ask questions and learn. Most important point is that you grow 'maters that you like, and that produce well for you. There are plenty of choices, so you might pick a new one or two each year, besides what your extension service recommmends.
'Maters come in two main growing styles: Determinate, or bush, get just so tall and then stop putting on height. Indeterminate just keep on a-growing until freezing weather does for 'em. (If first freeze is light, you still may get some production from the vines and roots.) Neither of these main types will fit in a 4-foot 'mater cage, but a dwarf container-grown 'mater *might*!
'Maters come in several groups by size/shape/use, too. Here are some "tendencies":
Cherry, grape: Little beggers that you can pop into salads (or into your mouth from a veggie tray, or the vine!)--Often grow in convenient clusters, so it is easy to pick 'em, even small.
Pear: Shaped like a pear, can be red, yellow, orange, etc. and often have a lot in common with the paste/plum. May also be tiny like the cherry, so you can cut in half and add to salads.
Paste/plum: Kinda oblong shaped and smallish, usually. These have less juice and more meat, so they cook down into tomato sauce, paste, and ketchup. I personally like them in salads, sandwiches, and in my hand as "eatin' tomatoes."
Slicer/salad: Oh, look! You slice these and/or put 'em in salads! *grin*
"Big, Beefy" (-steak, -master, etc.)/"Big" (-boy, etc.): These are the "big boys" -- a slice of tomato covers your whole hamburger bun--weather and green thumb permitting! ; ^ )
Heirloom: Can look like any of the above, and breeds true (which is why they are still around after a long time). Can also be stripey, odd shaped, or generally cute and colorful. May not be as disease resistant as some modern 'maters. (This is important if your garden/climate is subject to stress and diseases.)
Hybrid: The offspring of a deliberate cross by the grower between at least two 'maters that have good qualities. Often the "workhorse" of the garden, with good production and, maybe vitally, disease resistance, depending on the variety. "F1" just means it had two different parents. Hybrids generally don't breed true, so you can't save seed - you have to buy it or breed it.
Resistant: Letters on the pack or label show what a given variety is known to resist. V, F, and other letters are standard shorthand for specific nasties that can attack 'maters. You can read about them, or else ask here.
Dwarf: The plant itself is a little begger, so it grows well in a large pot or other container. Fruit size/type depends on what it is a dwarf of....