Internet Protocal stands for IP Address. So when someone says "IP" this is what they are referring to. The address part of the IP address refers to a very unique series of numbers called octets - in fact so unique that two IP addresses don't exist at the same time.
This series of numbers, or octets, are all completely linked at the moment you are surfing the internet to all your online activity. For instance what websites you have visited and how long you were there for.
All hardware (your computer or mobile phone etc) that is connected to the network or internet will be automatically assigned an IP address by your internet service provider.
In essence this allows your hardware device to communicate with other hardware devices across the internet
Most IP addresses have four "octets" and may look like this 192.168.1.2
Ipv4 is the older protocol that was used before IPv6 came along.
IPv4 doesn't hold as many IP addresses than IPv6 does. IPv6 can produce trillions of unique addresses.