Modules : About Modules : Module Types : Payload Modules

Payload Modules
A payload is the shell code that runs after an exploit successfully compromises a system. The payload enables you to define how you want to connect to the shell and what you want to do to the target system after you take control of it.
A payload can open a Meterpreter or command shell. Meterpreter is an advanced payload that allows you to write DLL files to dynamically create new features as you need them.
For more information on Meterpreter, see the Meterpreter User Guide.