Is it an encyclopedia or a social network? Without considering both aspects it would not be possible to understand how a worldwide army of editors created the largest online knowledge repository. Wikipedia has a consistent set of rules and it responds to many of the User Engagement Framework attributes, and this is why it works. In this paper, we identify these confirmed attributes as well as those presenting problems. We explain that although having a strong editor base Wikipedia is finding it challenging to maintain this base or increase its size. In order to understand this, scholars have analyzed Wikipedia using current metrics like user session and activity. We conclude there exist opportunities to analyze engagement in new aspects in order to understand its success, as well as to redesign mechanisms to improve the system and help the transition between reader and editor.