Older Wifi uses 2.4 GHz; since 802.11n came out years ago it also uses 5 GHz. Generally 5 GHz frequencies are recommended, when you have a choice, because usual

Older Wifi uses 2.4 GHz; since 802.11n came out years ago it also uses 5 GHz. Generally 5 GHz frequencies are recommended, when you have a choice, because usually there is less interference. While we're at it: In the 2.4 GHz range there only are 3 non-overlapping channels: 1, 6, 11. I think 14 also is an option in some countries, not including the U.S.