ATP stands for Adenosine Triphosphate. This sounds like a complicated name, but when we break the name down, it's really a simple description of what makes up the ATP molecule. (***see attached pic***)
I don't know how in depth you need to know the structure of ATP, so let's keep it simple. There are two major parts of the molecule (one is called "adenosine" and one is the "3 phosphates"). If you know that the prefix "tri-" means "3", then you can see that the name ATP is simply just telling you about the make-up of the molecule.
AMP stands for adenosine MONOphosphate. Therefore, it's two major parts are adenosine and 1 phosphate (because "mono-" means "1").
The energy from ATP comes from the bonds between the phosphates. Think of the molecule like a battery. The more phosphate bonds, the higher charged it is. Therefore, ATP has much more energy to release and power cellular functions than AMP does. AMP is actually the bi-product of the cell breaking ATP's phosphate bonds to release energy from them and power cellular functions.
