Think of the Amps as of the quantity of electrical current.
RPi uses 750 mili-Amps so your power supply must be able to provide AT LEAST 750 mA.
If your power supply is able to provide more, that's okay, RPi will use only 750 mA.
I personally run my RPis off some 2 & 3A power supplies - with a more powerfull supply you have the advantage that you won't have significant voltage drops whe you connect more power-hungry peripherals.
3A PSU with no load: ~5.12V
3A PSU with only RPi: ~5.08V
3A PSU with RPi + 5400rpm USB HDD: ~5.03V at spinup then ~5.07V