The characteristic impedance of coaxial cables is dependent on the internal and outer conductors.
75 Ohm Coaxial Cable----TV Signal Transmission
Indoor wiring for TV reception, connecting high frequency equipment, internal wiring, power supply wire for power line transportation etc.
50 Ohm Coaxial Cable---Data Communication, Wireless Communication
Indoor wiring for wireless communication, connecting and internal wiring for high-frequency equipment, power supply wire for power line transportation etc.