Red lentil is known for it’s fast cooking properties. This is generally used in a mashed form to thicken curries. Red lentils are commonly used in North Indian cooking.
The Dal (split and peeled) form of Masoor is highly valued in fuel short India, for its short cooking time and flavor. It is often cooked with rice, as the cooking time is similar. The Red Lentil is very similar, but more characteristic of North America.
The photo shows Masoor Dal to the left, about 0.17 inch (4.3 mm) diameter, with whole Msoor in the center, about 0.22 inch (5.6 mm). To the right are North American type Red Lentil Dal, about 0.24 inch (6.1 mm) diameter, however, some imported Red Lentils are as small as the Masoor Dal.
The peeled and split versions of these lentils are sometimes called “Egyptian Lentils” which an inexact term, usually meaning Red Lentils, but is also sometimes applied Masoor, and even Brown Lentils.