When I type vim in xterm the program is not opened in its own screen, but in the very same I am writing commands in. Let me explain: for example, lets say I type in the terminal ls -l /usr/bin and get a big list of programs. After that I type vim and the program is opened, but if I scroll up I can still see the list of programs in /usr/bin. As far as I remember, when I opened vim it would start in a clean screen with nothing behind it, so if I wanted to go back to the terminal I had to quit. Why is vim behaving like this and how can I change it? 
Why is vim not being opened in its own screen?
fedora;vim;xterm