The Artemis mission will return humans to the moon by 2026. This mission has been delayed due to issues with the launcher, the landing unit and even the spacecraft carrying the astronauts. Even so, NASA already has plans to build a base on the surface of the moon and to realize it, a space cargo ship needs to be developed.
So NASA announced they will appoint SpaceX and Blue Origin to build the cargo spacecraft. SpaceX is expected to modify the Starship spacecraft that can carry up to three Toyota-designed lunar surface vehicles for JAXA according to mock-up images produced. The Blue Origin system can only carry one.
Two different systems were developed because NASA wanted to have options depending on the mission as well as ensure there was a backup system if one ran into problems. SpaceX needs to send a vehicle to the moon by 2032 while Blue Origin sends a habitat unit by 2033.