how to use playerprefs to make the second playthrough diffrent ?

so if you played undertale or when the darkness comes you would know what i mean but for people who havent played these games it basically when you play for the first time everything is ok and it seems like a new game but in the second playthrough the people in the game know me and have met me before and in the " when the darkness comes" the game knows my name so how do i do stuff like that?

@Sneakypizza5776 You could save these as bool values eg. bool firstTimePlaying and if it’s false on load then do your stuff.