I search for Uber Coupons and I see results coming up in table format, what are the parameters on which google is showing knowledge box in search engine page results? 
Is there any specific pattern Google Engine is using to show knowledge box?
seo;google;google search;serps
It would seem this is just one of Google's featured snippets. (from the About this result link in the bottom right hand corner of that snippet.)Where does the answer summary come from?The summary is a snippet extracted programmatically from a webpage. What's different with a featured snippet is that it is enhanced to draw user attention on the results page. When we recognize that a query asks a question, we programmatically detect pages that answer the user's question, and display a snippet as a featured snippet in the search results.:How can I mark my page as a featured snippet?You can't. Google programmatically determines that a page contains a likely answer to the user's question, and displays the result as a featured snippet.As to what are the parameters on which google is showing this - well, it's all part of Google's AI (black box) - so only Google really knows the answer to that.You can provide Feedback if this snippet was helpful or not.