An analogy is a comparison between two things that are usually thought to be different from each other, but that have something in common. Analogies help us to understand something because they are compared to something we already know. It might sound a little confusing, but a few examples will make it easier to understand. Learning analogies can help reading and building vocabulary. Learning tools, like a thesaurus, can be very helpful if you get stuck when trying to use an analogy.
A great way to practice analogies is with online games. You will find plenty elementary analogy games that will keep you entertained.