Hmm no ones actually answered the op's question so I'll have a crack.
A 4 port hub for example takes a packet in on port 1 and broadcasts it on port 2,3 and 4. To be able to work each computer needs either a manual ip address setting to it or a seperate dhcp server to allocate the address.
A 4 port switch takes that same packet but uses a built in address table to send it out only on the port that has the computer attached leaving all other ports quiet.
A router is a switch that it can take your main ip from ntl of 80.x.x.x and give each computer a local ip of 192.168.1.x and translate requests. This means that you have a hardware firewall in that 80.x.x.x cannot be hacked as its the router.
In essence don't be tight buy a router there cheap enough
