Wolfram Alpha is an answer engine which provides ANSWERS to structured queries (e.g captial of sri lanka), rather providing a ranked list of web pages that most popular search engines would do. This engine uses automated reasoning to infer other results which is most useful for users. Thought the inferences that the engine makes is not currently amenable for my knownledge as of this writing, it gives very useful inferences. For more information read this and this.
I explicitly made the error in search query; "captial of sri lanka" (captial rather capital) to show how inferencing is done on the context of the search query.