A power chord is a popular guitaristic term used to describe a chord that does not have a 3rd and only uses roots and 5ths and their inversions. Because a “power chord” has no 3rd it is neither major or minor, it derives its harmonic quality from its position or harmonic context within a key. It is in ubiquitous use and has been since the late 50’s but became even more popular with the event of the complexities of the modern overdriven amplifiers which drove the 3rd even further away.