Unlike "3G" and "4G" in the mobile phone world which refer to "third generation" and "fourth generation" mobile phone technology, the "2.4G" and "5G" numbers in Wi-Fi are radio frequency bands.
In general, one band router only supports 2.4GHz and dual band router supports both 2.4GHz and 5GHz. If you use a dual band router, you would probably see two similar names in the Wi-Fi list that one has a "_5G"/"-5G" suffix added (e.g. MyWiFi and MyWiFi_5G).
Below is the detail differences between 5GHz and 2.4GHz Wi-Fi. In a nutshell, the 2.4GHz band gives you longer range especially through walls, whereas the 5GHz band offers more channels that are less likely to be polluted with interference.
The 5GHz band has a shorter range compared to a 2.4GHz band because in radio frequencies, the higher the frequency the shorter its range. In other words, if you are using a lower frequency like the 2.4GHz, the distance it will cover will be greater than the 5 GHz band.
Further more, the lower frequency means the better penetrativity. If there are walls between your router and camera, the 2.4GHz Wi-Fi should have better performance than 5GHz.
A 5GHz network has a lower chance of picking up interference because most wireless devices such as Bluetooth devices, cordless phones, microwave ovens, and computers use the 2.4GHz frequency. To learn how to reduce the wireless interference on a 2.4GHz network, click here. It's a configuration guide for Linksys router, routers of other brands should have similar settings.
The Gigahertz (GHz) range that a wireless device is using does not necessarily determine the maximum speed of the wireless network. A Wireless-A device that runs on the 5GHz band can also support a maximum data rate of up to 54 Mbps, which is exactly the same data rate that a Wireless-G device running on the 2.4GHz band supports. The environment in which the network will be set up is what really should be considered.