Basically, the major difference centers upon the location of the hitch.
With a 'bumper'pull tow-behind trailer, the pivot point of the trailer is over 1 meter behind
the axle of the towing vehicle.
With a fifth wheel, the pivot point of the trailer is almost directly above the rear axle of
the towing vehicle.
This difference in pivot point location determines how the trailer reacts to the movement of the tow vehicle while turning and backing up. It is much easier for the trailer to follow a fifth wheel hitch than a 'bumper' hitch, so the trailer reacts more quickly to the movement.
Because the fifth wheel hitch is centered above the rear axle of the tow vehicle (usually a pickup truck), the amount of weight put upon the hitch can be significantly larger than a 'bumper' pulled trailer hitch.
There are many more differences,blow, but these are a couple of the major ones.
There is another post by THE RICHMONDS below asking the same question. You can get more info there.
There is a hitch (Pull-Rite) which moves the pivot point of a regular trailer to the rear axel point, so the towing differences are minimized.
If you have a pickup truck, you can pull either a 5th wheel or travel trailer. If you have any other truck (SUV, van) you can only pull a travel trailer.
5th wheels tend to be taller than travel trailers, a factor if you are tall, at the cost of greater wind resistance, side wind sensitivity and damage from low obsticles. Also, there is a steep staircase up to the part of the trailer (often the bedroom) which is over the truck bed. And that portion of the floor plan is usually does not have much interior height (because it has to clear the truck bed). Travel trailers are all the same level and mostly the same interior height.
Of course, your overall length with a 5th wheel is less for the same floor size, since some of it overlaps the truck length. Also, 5th wheels seem to have more storage than travel trailers.