It varies depending on the source material, but generally speaking...
Cold Pressed Oil: is just that. The seed/nuts etc. are ground and then squeezed to extract the oil. Small quantities of oil are achieved. Usually this is reserved for high quality oils, or oils that need no refining before use.
Hot Pressed Oil: Is the same generally, but uses heat (usually steam). The seeds/nuts etc.. are cooked using steam and then pressed to extract the oil. You get a much greater quantity of oil, but it is damaged by the heat. Often companies will cold press first, to get the higher grade material, and then heat press the left overs to get the cheap stuff, and reduce wastage.
In regards to heat pressed oils... I would not use them. Very few oils are good to have at high temperatures. If using oils for therapeutic purposes I always suggest cold pressed.
For cooking there are a few oils that are OK at high heats, you might as well save a few dollars and buy them heat pressed. Most are still better cold pressed. The oils will be far better for your health.
