The payload, which is the actual malware that the threat actor wants to run on the victims computers, is protected against reverse engineering and detection (by security software) This is done by adding code that is not strictly malicious, but only intended to hide the malicious code. Packers are usually short for runtime packers which are also known as self-extracting archives A protector in this context is software that is intended to prevent tampering and reverse engineering of programs.”]
Source: https://blog.malwarebytes.com/cybercrime/malware/2017/03/explained-packer-crypter-and-protector/