When you type a word or a phrase in a search engine, the output that will be shown to you a list of websites or documents related to your search word or phrase. For example, typing “speed of light” in the Google search engine would return the list similar in the image shown below.
Wolfram Alpha, on the other hand, returns answers to search phrases or questions instead of a list of related documents or web pages. Searching “speed of light” in the Wolfram Alpha search engine returns the figure below.
Not only that, it can also perform computations. For example, type “US dollars 1000 to Philippine pesos” would return the equivalent amount (see Figure below).
Wolfram Alpha is an answer engine developed by Wolfram Research. It is an online service that answers factual queries directly by computing the answer from structured data, rather than providing a list of documents or web pages that might contain the answer as a search engine would (Wikipedia).
And Wolfram Alpha can do a lot more than that. To know more about Wolfram Alpha, watch the videos below.