If you mean connect 2 cables together to make 1 longer cable then use an extender or an adapter. Just search for “USB extender” or “USB adapter”. There are different types depending on the types of plugs on the ends of the cables. But bear in mind that there is a limit on the total length of a cable - for USB 2 this is 5 metres and for USB 3 this is 3 metres.
If you mean connect 2 cables into a single socket so that they can all share the same interface then use a USB hub. These have a single socket into which you attach a USB cable, and connect the other end of the cable to a USB socket on your PC, for example. The hub will have upwards of 2 other sockets into which you can plug peripherals, such as keyboard, mouse, disc drive, etc. This is also a way of connecting 2 cables together to make a longer cable. It is also a way of going beyond the length limits stated above, although USB hubs have their own length limits.
One of the things that you can plug into a hub is another hub. This allows you to extend the cable even further. And at each hub you can also connect other devices as mentioned above. But bear in mind that there is a maximum current that the source USB socket in the PC can deliver. For USB 2 this is specified as 500mA and for USB 3 as 900mA. This power has not only to supply any hubs but also the devices attached to them. Some hubs are self-powered, i.e. use the power being delivered by the source device such as a PC. But if you are intending connecting several devices then it is best to use hubs that have their own power supply. (All this excludes the adapters that you plug into a mains supply to just provide power, for example to charge a mobile phone. These have their own limits that is stated on the adapter).
The maximum number of USB devices that you can connect is 127. I don’t know if anyone has tried doing this, but if you intend to attempt it then you probably need a bigger room than the one that you have!
