This lets you look at a word in context, see how common it is, see the style associated with it. Such a tool is a computer-specific tool that you may not be familiar with from learning English by more traditional ways, but it is worth spending some time experimenting with it and getting to know how to use it and harnessing its potential.
In addition to showing you a clear and objective picture of language use, it can help you with words that you are unsure of, which is of great use or grammatical words and, probably to a lesser extent with vocabulary. You can use it to compare you usage with that of native speakers or other learners and, once you get to know it quite well, you can use it to explore attitudes, the thought processes that lie behind the words.
Learning and Teaching