One very simple thing it does is help you understand hierarchical semantic relationships. So, for example, you could have

    sibling => 
        => brother
        => sister

Then you know when eg: parsing text that if you observe the symbol "sister" in one place and "sibling" in another, they could be the same thing. This kind of thing is used in the medical space where one doctor might discribe a problem using a general term and the next in a more specific way and you have to be able to match them.