Tomato growth habits
There are 2 different types of growth habits in tomato plants. Indeterminate or cordon tomatoes, and then determinate or bush tomatoes. There is even a half way tomato which is semi-determinate.. basically it can't make up its mind what it is!
Cordon tomatoes, also known as vine tomatoes are the plants which are trained up a single stem and secured to a cane or string. Occasionally you will find a lateral shoot coming out from the main stem at a leaf joint, (I call these armpits) you must pinch these out so that there is only one growing point at the tip of the plant. This type of tomato will just keep going up and up and the top lead shoot (the terminal shoot) should be cut off when you have 4 or 5 trusses of fruit. This will make sure your plant puts its energy into swelling the fruit rather than growing green stuff upwards! If you don't do this you will end up at the end of the season with 8 foot tomato plants with loads of little green marbles which will not ripen!
The Bush tomatoes (determinate)...er... you just leave them to turn into a bush! (it does exactly what it says on the tin!) You can tie them loosely to a short cane. These are usually the smaller varieties - but check on the packet.