ranch 就是一種農莊，大農場。一般是一個特別打的牧場。 A ranch is a large piece of property that someone owns in a rural area (countryside). A ranch often has cattle (cows), and in such a case it's called a "cattle ranch", (Former President George W. Bush's residence in Texas is known as a "ranch" because it's a rural house with a lot of land. But I don't think he has cows there, nor does he farm.) farm 就是農場 ，種田。

Thank you for all your answers, I learnt from them.

A farm is an enterprise to produce food. (cereal or cattle). A ranch is a small land where you can have some economical activity, but it is less important and sometimes is just a resting place.

I think they both could serve the same purpose ,both being a land to rear livestock and cattle and to cultivate food in general . The 'farm' however is more specialized in cultivating vegetables, fruits and plants ,while rearing some livestock such as poultry and other animals kept for domestic uses. The 'ranch' ,being more of an American term is usually equipped with the necessary personnel and buildings for rearing livestock ,cattles in particular.

In British English we don't say "ranch", but I'm not sure if in American there is a difference in meaning/size between the two... I'd be interested to know also :)