NAT Network Address Translation
The trick that lets 10 home devices share a single IPv4 address to the internet.
Your router has a public IP address facing out and hands out private addresses (typically 192.168.1.x) internally. When a device sends something out, the router translates it to its own public address, remembers the mapping, and routes the response back correctly.
The reason IPv4 still suffices, despite us having billions more devices than addresses.