Collagen filler is a naturally-derived filler product - previous collagens were from bovine sources (cows), human sources (cadaver) and porcine sources (pig tendon). Not very glamorous sources, but collagen is a protein and thus far science has not been able to come up with a synthetic one for use in the skin.
Because they are non synthetic, they tend to break down very quickly. Most patients saw a 3 month duration - some a little more and others a little less. Recently Evolence was on the market for a brief period and was to have lasted 6 months or longer, but the economy hit it too hard to stay so for now, we only have the bovine and human collagens.
Because the newer hyaluronic gels such as Restylane and Juvederm last twice as long, they've pretty much taken the place of collagens for primary wrinkle filling and lip augmentation, but you can still get collagen if you desire.