How to Automatically Generate Tab Completions

If i start typing a command, the letters are read until it's a command that's valid. As soon as i type d o i n g, it turns green. It auto generates completions for any programme on your system that has a man page. Ah, it's really easy to add your own completions. If i'm in a folder that i have been in before, so i type c d d ov, and i go to my overtired folder. So whatever i most often execute in that directory will auto complete. I missed those features any time i switche back to bash, which is what i used previously. Nice. Am i?