RJ45
PATCH CABLE Patch cables provide a short-range connection, while longer Ethernet cables (usually Category 5, Category 5e, or Category 6) are used to connect to a hub up to 100 meters away.
A hub or switch must be used to connect 3 PCs together. Two PCs can be connected using a single crossover cable.
A straight cable is used to connect a PC to a hub, switch, or router.
Crossover
You do not have to connect your router to your PC via ethernet cable, you can instead connect via wi-fi and your router must be connected to your hub.
In ethernet terms, a straight-through cable connects a client device to a hub, switch or router (straight-through meaning the connection is pin-to-pin, the opposite of a cross-over cable, which connects RX-TX and vice-versa).
The primary function of the Ethernet hub is to connect the different cable segments. ...
Yes you acn use a hub to connect your computers. Just connect a cat5 network cable from each of your computers to the hub. It doesn't matter which port you plug the cat5 cable into on the hub. they are all the same. Also, if you might be interested in making your own cat5 cables. I have added a link on how to do ths.
The "Crossover" port. (or MDI-X)
In general, no, you would not use a cross-over cable to connect a hub/switch/router to a PC. This is because the device itself has cross-over circuitry built into it, and if you used a cross-over cable you would be reversing that process. The net effect is that the transmit signal would connect to another transmit signal, when it should be connected to a receive signal.
The "uplink" port. If it doesn't have one, you will have to use a crossover cable.
You need to use a straight type of connection. 568A or 568B depending which type your network is using.