might be talking about the restriction on playing games offline with steam. unless its changed since last I checked if you want to play a steam game and you for some reason or another don't have access to internet, to launch a game in steams offline mode you have to have launched them at least once with internet connection which is kinda DRM because its limiting the use of some thing you paid for, that's my best guess.
@sumikii!
Narvonix more or less already said most of it, but DRM-free means you don't rely on external software when playing your game i.e. no need to log in (or stay logged in while playing) or be slowed down by third-party software, and no required internet connection (like Narvonix mentioned). It's just you and the game. Games requiring you to put a disc in your computer while playing can be argued to be an early form of DRM, but most probably find that level of DRM acceptable. Some games in the "pre-online library era" don't require a disc at all, such as Age of Mythology Gold Edition (AoM GE), which means they are completely DRM-free. No need to log in or anything, just double click the game icon (.exe to be exact) and you are good to go. All itch io games are, as far as I know, DRM-free; you only need to download a game, then you can play the game. Not really any different from AoM GE.
Steam isn't like that these days. On top of requiring you to log in, it also exposes you to the problems in the library that I listed in my previous comment. Furthermore, these aren't the only problems, they are just the ones I care most about myself. There is no way to get rid of these problems on Steam without also getting rid of wanted features. Hence, I have been buying DRM-free ever since the library update was made mandatory. That's why I suggest DRM-free purchases; you don't need to fear the DRM-software becoming super bad, like what has happened to Steam.
It might not lag for you, but it does lag for me and many others. Painfully so. No, there isn't a way for me to improve it without also getting rid of much desired features.
I largely agree with the achievements part of your comment though. There are some games that don't register achievements in offline mode, but most do AFAIK.
