[Pharo-users] Where to channel questions

Hi, I'm new to the Pharo community and I was wondering where to channel Pharo-use related questions. In the Pahro.org site it suggests to post questions on StackOverflow "If you have any question regarding Pharo, use StackOverflow <http://stackoverflow.com/tags/pharo>. Be sure to tag your question with the pharo tag, so that your question is not lost amongst all the questions on StackOverflow." But is also states that Pharo questions can be directed at this user list. What is the criteria to use one or the other?