sub key word or sub topic of search engine

When we do a search online, we input a key word, I prefer to call it a topic, to the webpage of search engine, and the search engine return what ever it thinks related to us.

Search engine should have the ability to identify the sub-topics. For example, if I input Mercedes Benz, the search engine should be able to provide me some sub-topics like "buying Mercedes Benz", "Repair Mercedes Benz", "history and information of Mercedes Benz". And if I input "weather forecast", the search engine should be able to provide something like "local weather forcast", "methods used in weather forecast", "history of weather forecast". If I input "deer hunting", I could get "skill of deer hunting", "places of deer hunting", "equipment needed for deer hunting"...

And the most important is that those sub-topics should be identified by the machine, not human. There are two place to get those informaiton, firstly, direct from the web pages, by analysis of those key words, the search engine should be able to know. Secondly, from the input of people.

The reason we need this is because we are not really clear what we are looking for when we input something to the search engine in many cases, especially we are looking for something we don't know. So those sub-topics could provide a panorama of certain topic. This will help people gather knowledge.