Lentils are tiny, lens-shaped dried seeds. The most widely available variety are grayish-brown, but there are also yellow and red varieties.
Before using, pick through them, discarding any shriveled lentils or bits of gravel. Place lentils in a colander and rinse thoroughly. Unlike dried beans and whole peas, lentils do not need soaking before cooking.
Like beans, increase the cooking time when lentils are prepared with acidic ingredients, like tomatoes or wine. Or add tomatoes, wine and salt when lentils are nearly done.