See it as a toolbox to build programs that attack other systems. Those programs are often called 'exploit', as they exploit a problem in an other system. During

See it as a toolbox to build programs that attack other systems. Those programs are often called 'exploit', as they exploit a problem in an other system. During exploit development some tasks tend to be always the same. For example, creating a network connection to the target. Metasploit enables you to write your exploit in a way that you do not need to reinvent the wheel and makes certain parts interchangeable like the 'payload' (code to be executed on the attacked system).