Burp Suite's Decoder module allows us to manipulate data. We can decode information that we capture during an attack, but we can also encode data of our own, ready to be sent to the target.
Decoder also allows us to create hashsums of data, as well as providing a Smart Decode feature which attempts to decode provided data recursively until it is back to being plaintext.
We can also send data here from other sections of the framework by Right Click -> Send to Decoder.