1) Lots more notifications.
If you post something, and someone later replies or posts a followup,
you might receive one or more emails telling you that has happened.
If you don't wish to receive such notifications, there are a couple of ways of
a) Unsubscribe from the topic
At the bottom of the page with posts, there are some drop down menus, one featuring a wrench icon.
Click there and choose "Unsubscribe topic."
b) Alter your notification preferences.
Open your "User Control Panel" (from the drop down in the upper corner of any page, by your name)
Then select Board Preferences tab,
check or uncheck the appropriate boxes, and click submit.
c) Another place to check is in the User Control Panel -> Board Preferences -> Edit Posting Defaults
the last item there is about notifying you when there are replies to a post.