A power supply, or PSU, is an extremely important part of any PC. See, this is the hub that will take 120-240v and covert it down to 12v, 5v, and 3.3v at high amperage for the GPU, Fans/Lighting, and CPU respectively. If this thing fails, it can take your entire pc with it.
It is for this reason that I do not recommend buying any PSU without first doing your research on it from a reputable source, such as Johnny Guru. This includes any units I recommend here.