Promoting a post allows the author to bring attention to a particular post and bring it to the top of the main blog page. Promoting a post also subtly highlights the post with the primary theme color, and a loudspeaker icon will mark this as a promoted announcement. To promote a post, open it in the Post Interface, click the Promote checkbox underneath the Post Editor, and click the submit button. 

De-selecting the Promote checkbox will return the post to its original location sorted by the Post Sort Date or the Date Posted.