As a new "rpmaker" here, can anyone tell me what is different from buying the game at Steam or at rpg maker official website?
I never used Steam. What is different? I heard something about buying at steam makes the game "limited to steam", what does that mean?
So this applies for MV and MZ, but not the earlier engines. If you purchase from the RPG Maker Web store, you get the standalone engine, which means you don't need Steam to run it, but your activation code will also activate the engine on Steam, if you do want to download it from there. This doesn't mean you get two activation codes, so you can't give one to someone else - it just means you can install the Steam version or the non-steam version.
But it doesn't work the other way around - if you buy it on Steam, you will only be able to run it through Steam, and will not be able to have a standalone version.
Whether you buy on Steam or buy on the web store and activate on Steam, Steam will save your key so you won't have to go looking for it. If you buy on the web store, your key is saved in your account, so if you ever need to reinstall/reactivate the standalone version, you can just look up the key there.
The other difference is that if you buy on Steam, Steam will take a nice big cut of the sale, and the developers will get less.