X4: Foundations' latest patch is in public beta testing now. It can be pretty fun, but not in the normal way. Depending on how far along development is, there's going to be bugs. While playing the game is still fun, there's another game going on: bug hunting.
A few bugs are easy, like, say, a typo in some text. You spot it, you report where it is, developer fixes it, all done. Some need more work, though. To take a made up example in X4, maybe you land a station and the game crashes. If that is happening to everyone, all the time, it's an easy problem to find. But what if it happens sometimes and not others? "Sometimes I land a stations and it crashes" isn't going to be that helpful. But, if you figure out that landing in a Magpie always crashes while other ships don't, that's a lot more useful. If you can provide a save game that's just before the crash and it crashes for you (and the developers) soon after it's loaded, that's very useful and will likely result in a dead bug.
So, basically, you get to spend hours and hours finding problems, but you don't have to fix any of them!
Of course, that's not all the betas out there. Sometimes beta testers are expected to just play the game and the game itself will report anything going wrong. Or maybe they are just doing it more for general impressions of how fun the game is, either so they can adjust gameplay or adjust who they target for marketing.
A few are clearly just demos being called 'beta testing' to try and get more people to play the demo. A "beta test" that's going to start 4 days before the release date, with crates full of game copies already in stores, is not a beta test.
Beta versions - Star Citizen comes to mind, it may never leave beta. Need a pretty good PC to play it though. not exactly optimised yet., It eats ram
That's still in alpha. Once they put it all together, maybe they'll call it beta.
, didn't that get named Buried Grenadecraft?