I will make the assumption that you have a surround sound or home theater receiver and start from there. There are 3 main home theater speaker setups which you will see termed 5.1, 6.1, and 7.1 channel surround. You will also see mentioned the terms Dolby Digital, DTS, and Dolby Pro Logic. Let's dispense with the latter first: if your receiver is only Pro Logic (only older receivers at this point) you do not need to worry about 6.1 or 7.1 surround. There are some other formats such as Dolby Digital EX, Dolby Pro-logic IIx, Dolby TrueHD, DTS neo:6.1, DTS-ES, True-Surround XT, and undoubtedly more.