You may be certain of what your major will be and stick with that major until graduation. If so, you're in the minority. That is why exploring is important.
Consider beginning a course in your possible major to get acquainted with study of that subject at the college level. The first course can help you decide whether the major you think you will choose is right for you after all. Your major may wind up being something you first took because distribution requirements dictated you had to.
Choose a major seriously, but not prematurely. You don't have to declare a major until the second semester of your sophomore year.