>>12637435The red section is the first stage "super heavy booster" or just "super heavy." The first prototype is under construction but it hasn't been tested yet. It will require nearly 30 engines which would outpace the current production of engines, and its final design is somewhat dependent on the final design of starship, the blue part.
Starship might be able to perform a single stage to orbit without superheavy on paper, but without any usable payload or landing equipment so it'd be pointless. It is designed to take off without superheavy from moon or Mars.
