Tomatoes come in different shapes, colours, sizes and growth habits.
A basic division is between upright (cordon) tomatoes and bush varieties. These are also called "indeterminate" and "determinate" vatieties (often abbreviated "ind" and "det").
Cordon (indeterminate) tomatoes grow as long vines that must be tied to some kind of support (a stake or trellis). I tie three or four long stakes together at their tops and plant one tomato plant by each one. Indeterminate tomatoes do not stop growing and often they are stopped off by pruning the tops late in the summer. They also have to be pinched so they don't grow too bushy. Pinching tomato plants means removing the side shoots. You can let one or two side shoots grow, depending on how much space you have for the plant and how big the leaves are for that variety. It's easy to pinch the side shoots with your fingers or with scissors.
Bush (determinate) tomatoes do not grow as tall and often top off the stem with a truss of fruits. Bush type tomatoes are often not pinched, but for varieties that are too bushy you might have to limit the number of side shoots. Most bush tomatoes still need some kind of support so they don't fall over. There are bush varieties of different sizes - some varieties grow up to 120 cm tall, while micro dwarf tomatoes in many cases only grow 30 cm tall.
The leaves differ between tomato varieties. The length and width of the leaves differ, and also how many leaflets they have. Some varieties have wide and long leaves, and others have thin leaves. Some cultivars have simpler leaves with fewer but larger leaflets and are called "potato leaf".
Tomato cultivars also differ in how long their growing season is, i.e. if they are early or late. They also differ by how tolerant or sensitive they are to cooler weather and if they are suitable for growing outdoors or in a greenhouse, or if they can grow in exposed locations or need more sheltered locations.