With Google frequently updating its algorithms, it might be difficult for webmasters to keep up with their Search Engine Results Page. Google has multiple SERPs and there are chances of some of the elements appearing only when your search is shopping-oriented or local, or if Google has a direct answer for it.
Moz team has created an interesting infographic on Mega-SERP: A Visual Guide to Google. It is a single result page with different elements appearing together.
