Last year I wrote a post titled Google on Finding Entities: A Tale of Two Michael Jacksons. The post was about a Google patent that described how Google might tell different entities apart that shared the same name. The patent in it was filed in 2012 and granted in 2014. Google was also granted a new patent on disambiguating entities this week, which was originally filed in 2006. It is worth looking at this second one, given how important understanding entities is to Google.
It contains a pretty thoughtful approach to understanding and distinguishing between different entities within documents and queries.