i found out that the /usr is 100% full when i check the system information via cpanel. What does it mean and how it gonna affect the performance of the server ? I'm a newbie when it comes to server stuffy and do i need to inform my webhost abt it?

Can anyone advise ? Thanks

Well, you're webhost is probably already aware of it, but more than likely, all your files are stored in either /home or /var/www which probably isn't full, so you won't have to worry about having room for your files. That's just how your host decided to partition the drives leaving no excess in /usr.