The hem at the bottom of a T-shirt

Hemming, or a hem, is a type of finish that is done on the bottom of a garment.

The hem of your trousers is where they meet your shoes. The hem of a dress is the bottom edge of the dress.

The hem is not a seam in the sense that it does not join two parts together. Rather hemming is used to finish the fabric edge and prevent it from fraying.