Salad, the simple greens are anything but simple. There are basically four types of lettuces:
Lose Leaf Lettuce is probably the biggest category of greens. It can have green or red leaves and tends to be the most bitter.
Iceberg Lettuce is a ball of moist, crisp but not especially flavorful leaves.
Romaine Lettuce is long, moist, crunchy leaves and somewhat bitter.
Boston Lettuce is a well-defined head of leaves that is soft and tender.
I prefer to mix various greens together thereby getting a better texture and taste. There are many different varieties of greens that you can also use such as sweet chard, mustard greens, spicy arugula and radicchio. Of course you will need some extra virgin olive oil, vinegar, or lemons. I really am hooked on balsamic vinegar on my salads.
Besides your basic salads and dressing, you may start building a bigger masterpiece by adding vegetables, or fruits, nuts or croutons, and even meat, fish, pasta, cheese, or whole grains. Salad has no limit.