Many philosophers describe science by providing a laundry list of techniques that scientists use and by stating certain properties that all scientific theories must have. You have no doubt heard, for instance, that science advances itself through making observations, which in turn lead to theories, which in turn lead to more observations, and so on. You have also heard that scientific theories must be falsifiable and must make new predictions. All of this is true. Unfortunately, it doesn't do far enough in putting into plain language just why science is so universally applicable.
Scientists seek to build the most reliable understanding possible of how the universe worked.
During this process, we have learned from experience that some kinds of evidence are more reliable than others. The scientific method is merely that collection of tools and procedure which, when correctly applied, gives us information that is as reliable as possible. Let me illustrate. Pressing your palm to the child's forehead would tell you that the fever was high, but it wouldn't tell you just how high. To be accurate, you would need quantify the fever.