Every tomato description will mention whether it's determinate, or indeterminate. By nature, tomato plants are branching vines that continue to grow and make fruit as long as the weather is above freezing. That natural tomato habit is called indeterminate--there is no set (determined) limit to the plant's life or size.
Determinate tomatoes do have a limit. They have been selected for a mutation that limits them to a shorter size, sometimes called a "bush" tomato. Most full determinates have also been selected to make all of their fruit at once, then quit. That is useful if you want a single, big harvest to sell, freeze, or can. This usually comes at some cost in flavor, and most of these tomatoes also have firm flesh and tough skins to help them survive shipping in good shape.
Semi-determinate plants stay short and manageable, but do not set all their fruit and then die. They continue to make fruit until frost. Some older market varieties, a few old heirlooms, and the dwarf tomatoes all have this short-vine habit.
There are several terms for the size and shape of the fruit. Cherries we all know. Saladette is the next size up--about 2" across. These are the ones usually quartered or sliced for salad. Inside, they are juicy, with a firm center. Most of the early and extra-early tomatoes are this size. Saladettes are available in many shapes, colors, and flavors, and usually have a very high proportion of unblemished fruit. The photo above left shows a pink saladette type.
Large, full-size tomatoes can be divided into juicy types and true slicer types. Heirlooms and varieties with outstanding flavor can be of either type.
The "juicy" types look somewhat like a wheel when sliced; they have spokes of firm flesh with large "locules" in between that are full of juice. (This is also where the seeds are located.) These are great for salad or slicing, but can be too juicy for a sandwich or if you want the slices to hold together. Saladettes and many large tomatoes have this structure. The center photo by Karen Morton clearly shows the spokes of firm flesh and the locules full of juice.
True slicers have a different structure. They are just as juicy as "juicy" types, but the juice is more contained, in very small locules scattered all across the surface of the slice, instead of in 4 to 6 big voids. The flesh is tender and has a silky texture. So you have a meaty but tender slice dotted with small flecks and pockets of juice/seeds which are less likely to fall out or drip. Many of the most famous heirlooms and taste-test winners are of this type. They do not ship well because their flesh and skin are more tender than other types. The Pineapple tomato shown at right has the meaty texture and intricate structure of the slicer types, with dozens of tiny juice pockets throughout its yellow and red bicolor flesh. Brandywine is another of this type.
I've read over and over that paste tomatoes are drier and less juicy than all of the above types, but experience doesn't bear this out. It is certainly true of modern processing paste tomatoes like Roma. Heirloom paste types actually vary quite a bit in juiciness, but they do share a few important traits that make them better for cooking and sauce. The most important is that they peel easily. Modern processing tomatoes are peeled by machines or chemicals, but heirlooms were selected for hand peeling, and they all peel very easily. Usually, they also slip the vine leaving their calyx and stem behind, saving labor in de-stemming. Another important trait for traditional sauce or paste tomatoes is that they melt into a smooth, creamy sauce without a blender or food processor, instead of separating into very firm flesh and very watery juice.
A typical sauce tomato would be Italian Heirloom. It peels easily, and as soon as you lay pieces into a hot pan, it melts into a sauce with good body, creamy mouthfeel, and smooth texture. It will still need to be simmered to evaporate the juice and thicken the sauce, but it will be a sauce, not chunks of tomato. Most heirloom slicers have this trait as well--they make excellent quick fresh pasta sauces.
A typical canning tomato would be Rutgers. It holds its shape even under high heat. When you open the jar, you can take out whole tomatoes surrounded in almost-clear juice. This is a prized trait if you want whole tomatoes for the freezer or in jars for the winter. It will also stay chunky and firm if diced for pico de gallo salsa.
Drying tomatoes are a special type that is usually pretty tasteless fresh, and has little juice. In Italy, these were dried on the roof of the house, or in a sunny courtyard. If you have a dehydrator, almost any tomato can be dried. One strategy is to use slicers. Another is to use juicy types, and let the juice drain out in a bowl or colander before putting on the drying tray. Another is to use cherry tomatoes, just cutting them in half. I prefer to use paste tomatoes, cut in lengthwise slices. But I don't do much drying--I'd rather have jars of salsa and boxes of frozen pasta sauce. It all comes back to what you will actually use.
Ready to look at some tomatoes? Here they are.