It'll be hard to explain if you don't know about wrestlers from close to 2000 so I'm going to have to assume you do.
Back in 1999, Shane McMahon had booted his father, Vince McMahon, from the head spot of the corporation, saying that he had lost his toughness and was no longer vicious. Shane agreed to merge the Undertaker's Ministry of Darkness with the Corporation to create the Corporate Ministry to take down their common enemies, the Rock, Stone Cold Steve Austin, and now Vince McMahon.
Undertaker had claimed to be serving a higher power, embodied by a cloaked person believed to be stronger than the Undertaker. After many months of fighting between the Corporate Ministry and the resistance called the Union (made up of about 4 wrestlers and Vince who were semi allies with the Rock and Stone Cold), the Higher Power was revealed to have been Vince McMahon all along, and that the whole thing was a plot by him to eliminate Stone Cold once and for all by making the Corporate Ministry. This was kept secret from everybody except Undertaker, which is why Vince says he even fooled his relatives.
In case you want to know how this worked out, it didn't, really. Quickly after the reveal, Vince's wife and daughter announced Stone Cold as the new CEO to the WWF, leaving Stone Cold with 50% control of the company and Vince and Shane with 25% each. In the end, Vince and Shane defeated Stone Cold at the next pay-per-view in a ladder match for his 50% control of the company.
Story told by my hazy 1999 memories and the help of a quick skim of a wikipedia page.