Google it , you will understand.
I can only tell you basic purpose :
- When you host a game server, any multiplayer game , your ip changes everytime you restart the router. So your friends etc will have to be told the new ip everytime your router restarts or disconnects. So in order to get a fixed/ permanent ip where ur friends can join the game anytime , you need a static ip. That's how I will be benefitting from a static ip.
Other than that , it is used for file FTP , file transfer protocol , etc , to share a file using your ip with others. Other people simply connect to your server through that ip and download files. But if you dont have a static ip , it will change all the time and people wont be able to download things from your server.
there are many other uses but these are all I can think of right now...