Bloodborne has a rather extensive set of online gameplay modes, and online servers need to be maintained to work properly.

Via in-game announcement, Sony and From Software have disclosed that its new PS4 exclusive's servers will go down for regular maintenance every Wednesday from 8:00 PM to 11:00 PM EST., as you can see in the screenshot below.

Of course the game can be played both online and offline, and the offline mode will remain unaffected by the scheduled maintenance, letting you play the game by yourself to your heart's content.