Answer:
NAT
Proxy
IPv6
Step-by-step explanation:
Network Address Translation (NAT) allows a local area network (LAN) to connect to the internet using only one external IP address. The LAN addresses (typically 192.168.x.x) can be used over and over again.
A proxy is a computer that makes requests to the internet on behalf of the computers on a LAN. It is a more restricted flavour compared to the NAT, but the effect is the same.
IPv6 is a new addressing scheme that will use a 48 bits address space rather than a 32 bits address space of IPv6, and that would provide plenty of addresses.