The stringers are the supports on either side of each step, they are what hold your stairs up! There are many styles to choose from:

The tread is checked in to the stringer, this can be open or closed.

The stringer is cut to the shape of the tread and riser and can be open or closed.

The stringer is in the centre of the stair, this creates an open 'floating' look.

The stringer is in the centre of the stair, this creates an open 'floating' look.

In this closed style, the stringer is not visible