These numbers refer to two different “bands” that your Wi-Fi can use for its signal. The biggest difference between the two is speed. Under ideal conditions, 2.4 GHz Wi-Fi will support up to 450 Mbps or 600 Mbps, depending on the class of the router. 5 GHz Wi-Fi will support up to 1300 Mbps.
Of course, there are some caveats here. First, the maximum speed you might see is also dependent on what wireless standard a router supports—802.11b, 802.11g, 802.11n, or 802.11ac. You can learn more about how those standards affect things in our guides on whether you need 802.11ac and whether you should upgrade your wireless router.
The second big caveat is that important phrase we mentioned: “ideal conditions.”
The 2.4 GHz band is a pretty crowded place, because it’s used by more than just Wi-Fi. Old cordless phones, garage door openers, baby monitors, and other devices tend to use the 2.4 GHz band. The longer waves used by the 2.4 GHz band are better suited to longer ranges and transmission through walls and solid objects. So it’s arguably better if you need better range on your devices or you have a lot of walls or other objects in the areas where you need coverage. However, because so many devices use the 2.4 GHz band, the resulting congestion can cause dropped connections and slower-than-expected speeds.