Cottage cheese is a fresh (as opposed to aged) cheese akin to ricotta, queso fresco, and paneer. It's made by curdling milk and draining off the majority of the whey. This results in fluffy loose curds with a mild, slightly tangy milk flavor. Cottage cheese is typically made with cow's milk, but goat's milk, sheep's milk, or any other kind could be used.
That mild flavor and soft texture make cottage cheese a boon when it comes to cooking. This cheese doesn't melt, but the curds tend to dissolve into the background when mixed into a batch of muffins or used to round out a casserole. Because cottage cheese tends to be low in fat and high in protein, as dieter's have discovered, using cottage cheese is a way to bump up the healthiness of a recipe without greatly changing its flavor or texture.
To give you some ideas for how to use cottage cheese in your cooking, take a look at these dishes:
• Chickpea Casserole with Lemons, Herbs, and Shallots • Alsatian Cottage Cheese and Onion Tart • Lighter Stuffed Pasta Shells • Graham Cracker-Crusted and Pistachio-Flecked Cheese Torte • Quick Cinnamon Rolls • Heidi Swanson's Cottage Cheese Muffins
If you're interested in making your own cottage cheese at home, David Lebovitz has a great tutorial:
How do you cook with cottage cheese?
Related: On Making Soft Cheeses at Home