50 ohm feed line to GPS antenna
50ohm impedance refers to the geometry of a transmission line.

Coaxial cable is a popular type, with a thin central wire in a larger tube, spaced with plastic insulation. The geometry is maintained (as far as possible, and electrically if not mechanically) through coaxial connectors.

Microstrip is another type, with a track on one side of the board, opposite a ground plane on the other. For FR4 (a common PCB material), 50 ohm line has a width of roughly 2 substrate thicknesses.

At 1.5GHz (roughly GPS frequencies), the wavelength is 200mm (in air, less in plastic). Once your connection is less than a tenth of a wavelength long, so less than 10mm or so, you can often get away, without losing too much signal, with an unmatched connection, for instance a narrow track or piece of open wire. But it will be better if you make that track 2 substrate thicknesses wide!