Three phase power comes in two flavors.

Star and Delta.

Star has 4 leads - 1 for each of three windings, and 1 neutral which is the common connection point for each winding.
So for low voltages, this arrangement gives 208 volts between any pair of hot leads, and 120 volts from any hot lead to neutral.

Delta has 3 leads.
This arrangement gives 240 volts between any pair of leads. There is no 120 volts, unless a winding has a center tap.

I've omitted the ground wire in both cases.

rivets