What is the purpose of more than one TV Tuner PCI Card?

I bought an 05 alienware DHS at a yardsale for 150 bucks...over 5000 worth of equipment. that aside, It came with three TV tuner cards and i have no idea how to hook them all up to be compatible (using S-Video) with my television. How would i hook all three cards up? are they even needed? thanks!