Remote Access Tool is a piece of software used to remotely access or control a computer. This tool can be used legitimately by system administrators for accessing the client computers. Remote Access tools, when used for malicious purposes, are known as a Remote Access Trojan (RAT). They can be used by a malicious user to control the system without the knowledge of the victim. Most of the popular RATs are capable of performing key logging, screen and camera capture, file access, code execution, registry management, password sniffing etc. RAT can also be called as a synonym for backdoor, which includes a client and server program. The server or the stub program, if installed in the compromised system unknowingly by the owner of that system, then it is called as a Remote Access Trojan.
source : https://ijritcc.org/index.php/ijritcc/article/download/431/431/