to clarify your question a bit further, there are two types of accounts basically a steam account and a non steam account. If you create an account through steam you can only log in through steam, you cannot log in that account through any other platform, ps3, ps4, or pc. For the standard account (non steam) if you start playing on pc and later get a ps4 and decide you want to play on ps4 you just need to by the ps4 version and register it to your account and you can log in with the same character on pc or ps4. So in short steam characters can only play on steam and nothing else. Standard (non steam) characters can play on pc, ps4, or ps3 (you just need to buy each version of the game once and register it to your account) but they cannot log into steam. Hope this helps.