Ubuntu (and Debian) come with many "alternatives".

The system offers many editors, browsers, compilers, shells, etc. Just have a look at the large selection under /etc/alternatives.

ls /etc/alternatives

Under Unix, one can create soft links to soft links to soft links to an actual file. The alternatives work in that way. The soft links defined in the /etc/alternatives folder are pointers that one can change to make his/her system more likeable.

To change one of these alternatives, Ubuntu offers the update-alternatives script. For example, if you don't like Nano, change your editor with:

sudo update-alternatives --config editor

The function will give you a list of all the alternative available on your system and give you a chance to enter a number representing the editor  you'd like to use.

This works with all the systems that properly access the editor as /usr/bin/editor. This is a soft link to the alternative of the same name. That alternative then points to the real thing. For example, /usr/bin/nano or /usr/bin/vim.

For more information, check out the manual page of update-alternatives. It's pretty complete.