Basically, you'll play a bunch of 4 player games. The people who get third and forth place in the game get a 'strike'. Like in baseball, 3 strikes, and you're out (of the tournament). Last man standing wins

Right. Basically, if these are the rules (which they usually are) you'll be guaranteed a minimum of three rounds of pinball.

The format has some advantages...you don't spend time or money qualifying, so the tournaments generally run quicker. The venue gets less crowded as the scrubs strike out and leave. I guess the disadvantage is that you are only guaranteed three games of pinball, but then, if you have a crappy night it's nice that you can just go home instead of hanging around.

Downside being sometimes you get spanked right off the bat. Sometimes the tournament isn’t big enough you get paired up with someone who YOU KNOW is way above your skill-level so it’s feels like you’re walking in to some rounds with a strike.

Ideally you can pair like-skilled players so they all collect strikes. By the time it gets to last man standing even if it’s a very skilled player, you can have a bad ball and get knocked out.

Does not require 4 player games.

2 player games will work.

Or three player too, but four is the standard number

Number of strikes is variable as well. Obviously a three strikes has three but I've played in ten strikes progressive where 2nd gets a strike, 3rd gets two strikes, and fourth gets three strikes.

Matchplay refers to the 3 Strikes format as Knockout Tournaments.