A Fillet is the curved juncture of two surfaces that would otherwise meet at a sharp corner or edge.

While modeling a part all sharp corners and edges should be filleted. As can be seen in the example before and after animation to the right, all sharp corners and edges have been filleted, including even the smallest corner features. However one edge around the perimeter of the part has been left sharp, this is the parting line of the part which will be discussed in the “Parting Line” module up next.