A couple of notes to add to AngloItalian and David's info:
1) What makes catch wrestling unique is that it's a legitimate contest but allows both pins (usually for a three count rather than amateur's one) and submissions. That sounds like it makes no sense as they are such different targets, but in reality going for a pin will often force the opponent to bridge/push out, exposing a limb that can then be snatched in a submission.
2) Kev Lloyd from the video David posted also works as a pro wrestler and has done training seminars on adapting competitive catch wrestling for "performance" pro wrestling.
3) I interviewed Kendo Nagasaki a few years back (sadly after I'd done the book) and he talked quite a bit about his catch background:
The book also reveals Thornley’s extensive time training in catch wrestling at the infamous Snake Pit in Wigan. He notes to FSM that “One only uses [submission] wrestling when you want to put somebody in their places you might say. You only use what you would call submission wrestling if somebody decides they're going to be awkward with you.”
Such skills did prove useful at the start of his career when promoters wanted to push the masked character to a far greater degree than your typical rookie, including overcoming veterans. “My biggest problem was with the old guys. I’m only 22, 23 and if I had gone in as Peter Thornley and I gone on with Jim Hussey... Well, I probably wouldn't go on with Jim Hussey in my first few matches to start with and if I did, Jim Hussey will probably be beating me as a newcomer in this business.
“So I was in a unique position. I came in with a mask and unknown from the public's point of view, but some of the wrestlers knew I was this 22 year old who was green as grass as far as show wrestling was concerned, but they got a rumour that I've been to Wigan and that buzz went round. A lot of the old timers thought ‘Well, we'll try him’ and a lot of that went on but I turned out to be a lot better than they thought I was.
“My early career was based on fighting my way up the ladder and making sure that I even got a bit of the show because these old timers would steal a bit of the show off like you wouldn't believe. Geoff Portz and Dennis Mitchell, people like that were show-nickers: if you went in and you weren't prepared to force your hand a little bit, you wouldn't get anything. You'd come out of there and you'd done nothing except got your hand up at the end perhaps if you were lucky.
“So for the first year and a half of my career I was sort of building up a reputation and Jack Atherton used to feed me occasionally with lads that he thought we weren't going anywhere and let me loose on them so that I could establish myself as you might say. And he used to give me extra few quid if I had a bit of blood flowing.
“So then I got over this first year and a half when I was not really in with the top lads so much. They kept me away from them and then I got entered into tag matches with Count Bartelli to quiet me down because I got a bit of a reputation of being dangerous to be honest. Geoff’s job was to sort of drag me out of there if I was getting a bit too ambitious and that worked well because that gave me a bit of an inroad into the show business [side] where the top lads like Steve Viedor and people like that were starting to trust me and I could get in with them and they didn't not to expect me to do anything silly.”
“Then I got calmed down a bit and I realized that, you know, you've got to earn a living out of this business, you can't go on like I was. So I calmed down a bit and then sort of got introduced into more and more of the top guys. And then as time goes on with Kendo Nagasaki, of course it becomes a 100 percent show. When I came back the second time (in 1986), we used all the gimmicks you can think of, throwing salt and talking to ancestors and doing all these things. That was total gimmick, wasn't it?”
Thornley notes that even as his in-ring style evolved, his reputation still preceded him, causing some wariness that may not have been justified. “Those reputations last, they don't die. You're not as capable when you're 36, 40 years as you were when you were 26. You’re not but your reputation still is there and people are still a bit wary – ‘Is he as good as he was?’ and some might try you out but a lot don’t. You can't keep that edge. I don't care who you are or how good you were you. If you're going to be what you might call [real] wrestling fit, you can't be on the road traveling up and down the country and keep that edge. You can have the skill and the knowledge, but if you get somebody younger with that same skill and knowledge, you've not got a cat in hell's chance.”