STS-111, in addition to providing supplies, rotated the crews aboard the International Space Station, exchanging the three Expedition 4 members (1 Russian, 2 American) for the three Expedition 5 members (2 Russian, 1 American).
The Multi-Purpose Logistics Module (MPLM) carried experiment racks and three stowage and resupply racks to the station. The mission also installed a component of the Canadarm2 called the Mobile Base System (MBS) to the Mobile Transporter (MT) (which was installed during STS-110); This was the second componenet of the Canadian Mobile Servicing System, or MSS. This gave the mechanical arm the capability to "inchworm" from the U.S. Lab fixture to the MBS and travel along the Truss to work sites.