One of the main components of your computer is your PSU (Power Supply Unit). Obviously, it connects from your wall socket via a cable, and then it transform the current from the wall into different voltages and amps for your components. the following is a brief overview of the important things to know about your PSU:
PSUs output ranges from as low as 100W to 2,000W+, and varies in how much amps it delivers on the 12v rails. These values are very important when you think of your PSU, the maximum output of your PSU will directly determine what sort of hardware you are able to fit inside your computer. The amps on the other hand, will directly affect what kind of graphic card you are able to fit as more powerful cards require more power, both in watts and in amps.