A static IP address is one that remains fixed and never changes. The PC always sees the same address regardless if the session between the PC and ISP is broken or not. A Dynamic IP Address is one that changes over time or in the case of a Dial-up connection, when the user disconnects and reconnects to his/her ISP.
Static IP addresses
Static IP addresses are manually assigned to a computer by an administrator or your ISP. The exact procedure varies according to platform and the company that provides your Internet connection to you. Usually, if you have a business connection for your corporation or you are connecting a server for your office, you would be allocated one or more static IP addresses for your business.
These IP addresses are programmed on your routers and other network equipment supplied by your ISP or purchased by you.
Dynamic IP address
This contrasts with dynamic IP addresses, which is assigned either randomly, or arbitrarily assigned by a server using Dynamic Host Configuration Protocol (DHCP). Even though IP addresses assigned using DHCP may stay the same for long periods of time, they can generally change. In some cases, a network administrator may implement dynamically assigned static IP addresses. In this case, a DHCP server is used, but it is specifically configured to always assign the same IP address to a particular computer, and never to assign that IP address to another computer. This allows static IP addresses to be configured in one place, without having to specifically configure each computer on the network in a different way.
Also for some IP's depending on the ISP lease, eventually will change but not for a certain time period, could be days, week, months etc..even up to a year.