spectrum analyzer display

what is the unit for the vertical axis on the spectrum analyzer display? I saw it is dBm which is energy level. when i use the spectrum analyzer to check FM input signal, the vertical reading decreases with decreasing frequency resolution. So the vertical axis just display the total energy in that resolution. it is not evergy divided by resolution bandwidth. Am i right?

You are right. The displayed power is the total power in the resolution bandwidth. So large resolution bandwidth will give large power result.

dBm is NOT Energy Level..It's Power level.
Energy is the Integral of Power by Time.