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. Â There are two major parts of the molecule (one is called "adenosine" and one is the "3 phosphates"). Â 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.