There are two Library folders. One is at root level (you see it when you click on the Macintosh HD folder) and the other is in your drive space. Anything placed in your Library folder can only be accessed by you while anything placed in the root Library folder can be accessed by any user.
It is a good rule of thumb to place items only in your own Library folder and to leave the root Library alone - at least until you have some Mac experience behind you. Should you place something in your own library folder that chokes the computer it would still be possible to log into another account on the computer (assuming you had one - and it is a good idea to have one) but if you put something into the root Library that made the computer choke it might not be possible to (easily) fix the problem.