There are two spacecraft; the first is the crew habitat for interplanetary program spacecraft (CHIPS) and the second is the lunar lander (BULL). The main system housing these spacecraft, is the Gateway which stays in near rectilinear halo orbit (NRHO). The Gateway must constantly provide all functions necessary for humans to live on the moon for up to 10 years.
The Orion is used to travel from Earth to Gateway, then from there a crew of four astronauts will travel to the lunar surface using the BULL lander. BULL must provide life support for 6 days and can be resupplied at Gateway after exploring the Moon.
The final components include a power and propulsion element (PPE) that uses solar arrays for power and propulsion systems for boost and altitude control of the Gateway. Lastly, there is an orbit transfer vehicle (OTV) to move the BULL lander from Gateway to low lunar orbit (LLO).
The image below is the concept of operations and architecture. LEO refers to low Earth orbit.
