Brown lentils are simply whole red lentils. Whilst red split lentils are quick to cook in 15-20 minutes, these brown lentils will take longer - 35-40 minutes, ideal for warm salads, casseroles, classic vegetarian versions of bolognese, lasagne, moussaka, cottage pie and stuffing as they tend to retain their shape after cooking.
Lentils are one of the best sources for iron. Boil lentils in three times more water than pulse and avoid cooking with anything acidic- such as vinegar.
For more information on the nutrition, cooking times and some tasty recipe ideas with pulses have a look at this Real Foods Guide To Pulses.