Chances are you're visiting here because you died during the first hour of Nier: Automata and are wondering why you had to start the game over. If so, we have bad news: there are no saves during the early portion of the game.
It isn't until after you defeat the first boss along with about one hour of content that saving is unlocked. Because of this, playing on Hard your first time around isn't recommended as you might end up in a loop of repeating the early section, leading to frustration.
Once the save feature is unlocked, you'll be notified. From here, checkpoints are infrequent, but you'll be able to manually save at access points throughout the game. You'll know where these are as they will be denoted by a 'Saving Possible' message at the top right of your screen.
Save often, because Nier: Automata is a challenging game and takes no prisoners.