Curved acrylic nails are acrylic tips that have a C-curve. A C-curve is the curvature of a nail when looking at the tip head on; it is the arch of the tip.
This curve is obtained either by pinching the acrylic nail or using a C-curve stick or rod. A C-curve stick is matched with the size of the cuticle to give an optimal curve. The acrylic tip is then shaped to have the same curvature as the stick.
Curved acrylic nails are often referred to as talons or claws. The reason for this is because the tip does not remain flush with the nail but curves around the tip of the finger like the talons of many birds.