The Wilson 859922 Combiner/Diplexer is a coupler which allows you to combine two 600 Mhz to 960MHz and 1630 MHz to 2330 MHz feeds into a single signal or vice versa. It is most often used to combine signal from two single frequency amplifiers to be fed into a dual band amplifier. It can also be used to split signal from a multi band amplifier into 600 Mhz to 960MHz and 1630 MHz to 2330 MHz feeds. This could be used if you have two areas with people on different cellular networks, although this is rare.
The splitter has N Female connectors. Typically a 2ft cable is used to connect the diplexer/combiner to the amplifier. Any cable length can be used, but the total cable length in the system should be kept as short as possible to minimize attenuation. Lengths of coaxial cable can then connect the diplexer/combiner to the external or internal antennas.