Commercial farming involves farming for a profit. These farms can be arable (just growing crops), pastoral (just rearing animals) or mixed (both arable and pastoral).
The arable farms of East Anglia are a good example of commercial farming, as are the cereal farms of the central United States and the Canadian Prairies.
Subsistence farmers only produce enough to feed themselves and their family. This is the most common form of farming in LEDC's.
Some of them are nomadic, meaning that they move around the country using a piece of land for a while and then moving on.
Intensive farms generally take up a fairly small area of land, but aim to have a very high output, through massive inputs of capital and labour.
Extensive farming is the direct opposite of intensive farming. The farms are large in comparison to the money injected into it or the labour used on it.
The main types of farming that you would find in the UK are arable, dairying and hill farming. All of them are commercial.
The Common Agricultural Policy and other regulations have encouraged arable farming more than dairying or hill sheep farming, and this has led to many farms becoming mixed farms.
Most farming in Britain tends to be intensive although some of the hill farms of Wales and Scotland could be described as extensive.