Crypter is a tools used to encrypt a file to make it unreadable.
Most common type of crypter which can be found on the net is being used to make a virus fully undetectable by antivirus. It is coded by a programmer using language such as C++, vb.net, asm, delphi and autoit.
With crypter, you can actually do a lot of bad stuff aka hacking without even need to learn any programming languange. It makes hacking easy as 1,2,3.
Buying a private crypter cost a lot of money. My suggestion is try to code your own.