Internet Protocol (IPs) addresses are assigned to every machine connected to a network. When you want to communicate with any other machine in the network, you would need its IP address. Similarly, all machines that are connected to the Internet have an IP address assigned which uniquely identifies them.

Internet uses DNS (Dynamic NameServer) to assign a mneomonic (memorable) name to these IP addresses and DNS server acts like a Yellow Book or a diary which keeps a track of all the names and their corresponding IP address.

IP addresses are essentially of two types - Static IP address and Dynamic IP address

When a Static IP address is assigned to a machine, it remains throughout. While dynamic IP address changes whenever you restart the machine/ reconnect it with the network or after scheduled time. Dynamic IP address is frequently used.

Static IP address is needed when you want anything to be accessible with same IP address at any time - for example: Servers in a network, Websites, etc. Subscription to these are sold by Internet Service Providers. It helps in assigning various types of network policies to different set of machines in a Virtual Private Network.

Dynamic IP address is automatically assigned by DHCP in a network. When you connect to internet, you are provided a dynamic IP which changes everytime to connect with the internet or restart your modem.