The frontpage currently has six questions that were modified by Community:
Does anyone know what modifications were made and why?
This usually means one of two things:
There has been an automatic bump. This happens to questions which have positive (or maybe non-negative) score, when they have an answer or answers yet none of the answers has positive score or is accepted (that is, they are still in the "unanswered" list while having an answer). My experience tells me that if there are new answers to questions the system deems similar, then there's an increased chance that such bump will occur.
There has been an anonymous edit suggestion that has been approved.
The easiest way is to click on the "modified 2h ago" text, which will lead you to the last activity. If the last activity is something which was edited then it's the latter; if not see about the score of the answers and usually you can deduce the former.
(I only saw two Community labeled posts, and both were automatically bumped.)