The difference between the two is pretty simple: it all comes down to range and speed. 2.4 GHz has a longer range, meaning it reaches a lot further than 5 GHz Wi-Fi.1 However, even though you can connect to 2.4 GHz Wi-Fi from your basement, it will have a slower speed.1
5 GHz Wi-Fi is faster. But faster also means it won’t reach as far. Techie lingo aside, you trade one benefit for the other when it comes to your internet connection. Keep in mind that not all routers support both versions of Wi-Fi—many older routers only have 2.4 GHz, while newer routers usually have both.1
The same goes for devices. If you have a really old PC, it might not have an option for changing Wi-Fi frequencies. But your new smartphone very likely does. In order to experience the full benefits of 5 GHz Wi-Fi, you should use a device and router that supports it.