He was not as well known as many Superstars because his wrestling career was short and he spent a long time working in the backstage office, but to those who followed WWF/E for a long time, you may have seen him as one of Vince McMahon's Stooges AKA Patterson and Brisco who appeared on camera from time to time (often with a retired Sgt. Slaughter).
Most notably, he was WWF's first Intercontinental Champion, it was the second-tier singles title belt behind the World Championship.
Patterson also is credited with inventing the Royal Rumble. It's like a Battle Royal but instead of all 30 men starting in the ring, you start with two in the ring and the other 28 enter at one-minute or ninety-second intervals. This created more storytelling possibilities. If you were the first man to enter, you had to beat 29 other guys in a match that lasts an hour or more. If you were the last guy in, you only had to beat a few guys and last maybe five mintues. So in the weeks leading up to the event they would draw lots for placements in the match, they might hold a mini-tournament to get the coveted #30 spot, etc. The Royal Rumble match became the basis for one of WWE's "big four" annual wrestling events, the others being Wrestlemania, Survivor Series and Summer Slam.
The article above mentions Pat being the first openly gay pro wrestler, I'm not sure that's true, even in the WWE. It also says he publicly came out in 2014 but I think it was a well known fact since the 1980s at least.
My best memory of Pat Patterson was when he asked Black Jack Mulligan to crush apples in his bare hands. It was such a stupid way to try to show the strength of Mulligan’s “claw”, as the apples were clearly rotten, but it was one of the last barnstorming stunts I remember right before the WWF really took off. One of those golden moments between the quaintness of a regional Saturday morning tv show and the world wide phenomenon that the WWF would become.
I knew he was a retired wrestler turned announcer at the time which made it a bit sensational when an active wrestler (I think Greg Valentine) attacked him. I was new to the sport and was surprised when wrestlers would fight announcers. A great way to draw kids into the drama and Patterson played the role perfectly.