[Novalug] What is the name of this great feature in Ubuntu?

[Ben Creitz]

I have noticed that Bash in Ubuntu completes not only commands, but
options for many commands.  For example, when I say

  sudo apt-get i

and hit <tab>, the 'i' becomes install. When I then type

  sudo apt-get install sysv

and hit <tab>, I will get a list of all of the available packages
beginning with 'sysv'.  I have not seen this in other distros; has
anybody else?  What is this feature called?

-Ben