Of course, a jet engine doesn't reverse it's thrust. A jet engine only goes in one direction, forward. There are systems that mechanically deflect much of the thrust, sending some of it backwards. Older just use a manifold that moves over the exhaust. Newer ones have a sort of door that opens and the exhaust deflects more efficiently through a system of slots angled backwards.

I always like to see these working when I am flying in a seat where the jets are visible. Many times the pilots don't use "reverse", it is sometimes not working and isn't required to land the plane (spoilers and brakes are required however).

The 767 that deployed reversers mid-flight was the victim of a design flaw in the earlier 767s.