The grammar of your first language comes to you almost automatically. Listen in on a conversation between two four-year-olds:

This simple conversation features sophisticated grammar—the subordination of one clause to another, a compound object, and a number of adjectives—used effortlessly. If you are like many English speakers, you may never really have reflected on the details of how the language works. Paying close attention to how you put sentences together can help you understand the choices available to you whenever you write.