Now consider a long block.

It is as big as two squares, so it takes up spaces A and B.

The long block takes up spaces A and B. Nothing else can be in A or B while it is there.

Now consider a cup on square A.

The cup takes up space A.

Nothing else can be in space A while the cup is there.

The cup takes up space A.

Now consider Koa sitting in a chair.

Koa sits in one chair. Elsie sits in the chair beside him.

Koa takes up the space in that chair.

Elsie cannot sit in that same space while Koa is there.

She sits in the chair beside him, in a space of her own.

Big things take up space, like a chair. Small things take up space, like a bead.