The public IP is the unique address your connection uses on the internet. It is assigned by your provider and is what every website, app or service sees when you connect.
Who assigns it
Address blocks are distributed by regional registries (such as LACNIC, ARIN and RIPE) to providers, which pass addresses to customers. That is why IP geolocation usually points to the provider's region, not to your home.
When it changes
On residential connections the IP is usually dynamic: it may change after a router restart or a long session. Companies and servers typically use a fixed IP.
What it reveals
A public IP allows estimating country, region, city and provider. It does not identify a person, does not show your street address and does not give access to your device. Still, it is connection data: it is worth knowing yours, which you can do in the IP Checker.
Shared IPs
With CGNAT, several households share the same public IP. That explains why two neighbours can appear with the same address on the same site.