What is the difference between at and on?

Answer 1

Both are prepositions, but describe different locations between objects. For simplicity, I will 'X' and 'Y' for nouns.

When one says, "X is at Y," it means that the two are the same location in space. For example, "My car is AT my house." This does not necessarily mean that X is within Y, but simply means that, if one is located at 'Y', then one can easily locate 'X'.

When one says, "X is on Y," it means that X is touching Y, but is also above Y -- ie, further from the ground. Thus, to say, "My car is ON my house.", would mean that your car somehow went from being located on the ground to being on the roof of your house.

Further information: When one says, "X is above Y," it also means that X is further from the ground than Y, but there is no physical touching between the two. Thus, "The helicopter is above my house" means there is an object hovering in the air over your house; while, "The helicopter is on my house" means there is an object actually touching the top of your house.

Thus, you "Sit ON a chair" but you do not "Sit ABOVE a chair."