Just has a problem connecting an Ipad to bt home hub. One of the solutuons on the web was changing the ssid’s so they are not the same on the 2.4ghz and 5ghz connections. I have tried this and it seems to have worked. My question is in simple terms what did I do as I have no idea what an ssid is or why there are 2 ghz channels etc?
Keeping it simple would be handy 🙂

They are different channels for wifi. A lot of new routers and tablets support types.
2.4GHz is the usual standard, it has better range. But it has a limited number of channels, so likely to get interference from your neighbours wifi, or cordless phones, or microwaves etc.

5GHz is a newer version. It has more bandwidth, so could be faster. Also more channels, so less likely to get interference. But more limited range, it doesn’t pass through walls very well.

The SSID is basically the name of the network. If you give both of them the same SSID, your Ipad will think they are both the same network, and will automatically switch to which one is fastest or has the strongest signal.
But this doesn’t always work. ie if you are moving around the house, it may stay connected to the weaker one. Or it may frequently switch between them, which means you are losing the signal as it disconnects/reconnects.
Probably better to just pick one, and stick to that.