Payload
Whatever a launch vehicle is carrying that is not part of the vehicle itself - a satellite, a crew capsule, a cargo module, or an instrument.
Payload is the unit in which launch is bought and sold. A vehicle is advertised by how many kilograms of payload it can put into a named orbit, and that single pairing - mass and destination - decides which rockets a mission can even consider. The word also draws the line of responsibility: when something fails, whether the fault sat with the vehicle or the payload determines who pays and who is grounded.
Payload capacity is why the same satellite appears on very different manifests depending on its target orbit: of the 350 missions we track, a rocket that comfortably lifts a spacecraft to low Earth orbit (144 missions) may not reach geostationary transfer orbit (23) with the same mass at all.
The spacecraft bus, which is the structure and support systems carrying the instruments, and the payload fairing, which is the nose cone protecting everything during ascent.