what is the part called that i need? its the main hose from the engine

There are several types of hoses coming off the engine. The most common are Radiator hoses. There should be upper and lower radiator hoses and they would cause a coolant leak or potentially overheating. There are also heater hoses, by-pass hoses, evaporative hoses, fuel hoses, vacuum hoses. Would need more info to help you out.

Imagine , if you were to cut the hose open , what would come out? Gas , oil , diesel fuel , antifreeze , power steering fluid , brake fluid , washer solvent , transmission fluid ,...........or AIR? Does the 'hose' go from the air filter housing to the engine intake?