A gooseneck camper is attached to the bed of the truck with a mounted pin and jaw hitch. It's called a gooseneck because if the camper was stripped down to just its lower frame, the front portion would loosely resemble a goose's neck, arching over the tailgate area of the truck and into the truck's bed.
A travel trailer is attached to the rear of the tow vehicle with a ball and hitch.
Generally, a fifth-wheel camper is a bit more costly than a travel trailer with equal options and features. But of the two, the gooseneck typically has more living space and storage room.
A gooseneck is more maneuverable because the overall length of the trailer and the tow vehicle is less than that of a travel trailer with equal floor space. With increased maneuverability, it's easier to make turns. A gooseneck is more stable when towed.
A fifth-wheeler is more easily hitched and unhitched, in part because there's no fussing with low-to-the-ground connections. A gooseneck has a higher ceiling, providing a more open and airy feel as well as extra overhead storage.
A fifth-wheeler typically holds more fresh water and waste water, meaning you can extend your stay at campsites that don't have water and sewer hookups.
A fifth-wheeler has to be pulled with a pickup, and takes up space in the truck's bed. A travel trailer can be towed with a pickup, a sport-utility vehicle or a van. A fifth-wheeler is generally heavier than a travel trailer, requiring more power from the tow vehicle and possibly hurting fuel mileage. A gooseneck's top is usually higher than a travel trailer, and thus more prone to hitting something overhead. A gooseneck often has two floor levels and sits a little higher off the ground, both of which might be undesirable for people with disabilities.