www.yelp.com
We are considering the recommendations provided after the search and not the main search itself. (The main search recommendation seems to be very comprehensive and is detailed here - https://www.yelp-support.com/article/What-is-Yelp-s-recommendation-software?l=en_US)
The whole general population.
To serve customers with list of businesses by category in the area searched for along with its ratings. Additionally any search should serve up link of other similar businesses of interest to guide navigation till the desired business is found.
The goals of the business by improving the recommendations to be more aligned with user’s habits and history.
The site seems to have taken into consideration 3 factors in recommendation engine - location, rating and cuisine. It served up 3 recommendations - 2 of same price range and 3rd one of a higher price range.