Output of `yum list installed`, rightmost column: 

Most of them say `installed`, some say `@amzn-main`, and some say `@amzn-updates`. 

What is the meaning of this? It says `tmux` is `@amzn-main`, but I have been running it. So is it actually installed or not? 

I'm trying to compile `zsh` 5.0.2, but its configure script is complaining about not finding `ncurses`. `ncurses` is listed as `@amzn-updates`. I have been looking around the system for its files without much luck, and `sudo yum install ncurses` gives me 

```
Package ncurses-5.7-3.20090208.11.amzn1.x86_64 already installed and latest version

```