[twitter-dev] What exactly does the follow parameter to friendships/create do?

[Josh Bleecher Snyder]

Hi all,

I'm sure this is a stupid question, but my Google kung fu is failing me.

http://apiwiki.twitter.com/Twitter-REST-API-Method:-friendships%C2%A0create
describes the parameter thus:

* follow.  Optional. Enable notifications for the target user in
addition to becoming friends.

What confuses me is: What are "notifications for the target user"?

Thanks,
Josh