A dynamic IP address is an IP address that changes over time rather than staying fixed. Most internet users have one. When you connect to the internet, your ISP assigns your device an address from a shared pool, and that address may be different each time you reconnect or after a set period of time. 

This assignment process is handled through a system called DHCP (Dynamic Host Configuration Protocol). Your ISP essentially leases you an address for a limited time. When the lease expires, a new address is assigned, which may or may not match the previous one.

Dynamic IP addresses are the standard for residential internet accounts because they allow ISPs to manage a large number of customers without needing a unique, permanent address for each one. They work well for everyday browsing, streaming, and general use. 

If you need a consistent, unchanging address for hosting a server or remote access, a static IP address is the alternative worth considering.