What does 'apt-get install update' do?

There is no command like this:

$ apt-get install update
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package update

Any arguments given after install will be taken by apt-get as a package name. But since there is no package update, it will fail.

It attempts to install the package named "update".

As far as I know there in no package called update which the command apt-get install update should install.

May be they meant apt-get update which updates the apt cache.