In general terms, a router table consists of a flat table surface with a router attached to the bottom. The router is mounted with its base attached to the underside of the table and the bit sticking up through a hole in table’s surface. The table holds the router securely, leaving the woodworker free to keep both hands on the work piece during the cut.
Whichever type of router table you choose, make sure it is flat, smooth, slick, and stable. Flat and smooth are obvious. But why slick? Work pieces need to slide easily against both the table and the fence, creating the least amount of friction, so each pass is smooth and even. And stability is a major safety feature.