Nothing on a network can receive anything until it has an address — same as post. An IP address is that address: a number like 192.168.1.42 that identifies one device on one network at one point in time. Every website you visit, every message you send, is packets of data with a destination IP written on the front and your IP as the return address.
Reading the number
An IPv4 address is four numbers from 0–255 separated by dots. The useful intuition: it reads like a postal address from big to small — the early parts identify the network (the city and street), the last part identifies the specific device (the house number). Exactly where "network part" ends and "device part" begins is configurable, which is the entire subject of subnetting — a later stop on this trail. For now: left is neighbourhood, right is house.
Public vs private: the crucial split
Not all addresses are reachable from the internet. Certain ranges — most famously 192.168.x.x, 10.x.x.x, and 172.16–31.x.x — are reserved as private: usable inside any home or office, invisible from outside. Your laptop's 192.168.1.42 exists in millions of houses simultaneously without conflict, like every town having its own High Street. Your router holds the single public address your whole household shares, and translates between the two worlds (that trick is called NAT — it gets its own post).
This split is the first question of network troubleshooting made concrete: a device with a private address and no route out can talk to the printer but not to Google. "Can you reach things on your own network?" and "can you reach the internet?" are two different tests for two different failures.
Why there are two versions
IPv4's four numbers give about 4.3 billion possible addresses — which sounded infinite in the 1980s and ran out decades ago. IPv6 is the replacement: vastly longer addresses (they look like 2001:db8::8a2e:370:7334) with enough space to address every grain of sand on Earth many times over. The two run side by side today, which is why your machine typically has both. For beginners the practical takeaway is simply: IPv6 isn't a different concept, just a bigger address book — everything you learn about addressing carries over.
One habit worth building immediately: learn to find your own IP (ipconfig on Windows, ip addr on Linux). It's the "where am I?" of networking — the starting point of nearly every diagnosis you'll ever run.