This is a screen shot of the 1940 census for my grandfather Ernest Richard (Tut) Colvin. How does ancestry do this?
"Using the information from this record transcription, Ancestry searches for other records that may be related to the same person. The suggestions system also looks at people in trees to which this record has been saved to see if there are additional records saved to those people. These records are displayed here to aid you in finding other records that may help you in your research."
Happy ancestor hunting.