The C2V is a short-medium range UHF/high VHF antenna. The C4 is a long-range UHF-only antenna. "CJM" stands for ClearStream J-Mount which s the 20" universal mount that is used with some of the smaller antennas. Antennas Direct offers a variety of retail packages, some include, others don't, the CJM. Read the specific product listing.
You need to select the configuration (plus accessories, if needed) based on YOUR location and the stations in your area.