The reason "business" as an academic field is so vague is that you could end up in any of dozens of roles in any of hundreds of industries. (By comparison, a law student will usually become a lawyer in the legal services industry, and a medical student will usually become a doctor in the health care industry -- with of course exceptions for both.)
It might be more helpful for you to think about the role you'd like to play in your career -- for example a business major can be a specialist in marketing, accounting, human resources & organization management, or e-commerce (just to name a few). Simultaneously, think about industries that interest you -- for example, Hollywood, pharmaceuticals, automotive, computer software, or publishing.
Now, you don't need to be a "business" major in college to serve in a business role. A lot of marketing people majored in psychology, anthropology, or sociology, and a lot of financial analysts at Wall Street banks majored in non-business fields like chemistry, philosophy, or math. What a business major gives you is a broad preparation to take on a number of business roles in a wide variety of industries. For the most part, a liberal arts major will give you the same thing. (An exception is accounting, where you pretty much have to major in it in undergrad, and take some graduate courses, to work and advance in the field.)
One thing you should realize is that there is a business side to any industry, including medicine and law. For example, hospital administrators are performing a business function. Many law firms are large enough that they need professional human resources managers. Pharmaceutical firms and health care companies like Johnson & Johnson need professional marketers, project managers, and accountants just as much as they need chemists and engineers. And so on.
You might want to go to your school library and/or guidance counselor's office and check out a few books that might help you:
--The College Board's _Book of Majors_ describes college majors, and has a whole section of different business majors (including a general "business" major, but also specialities like finance and marketing). While the focus of this book is what you'll study in college if you major in these fields, the connection b/t major and careers is explored.
--Vault Guides cover various industries in depth, and usually make it clear which jobs within those industries are for "business" type versus for specialists from non-business fields. (For example, a business major will probably not get a job as a newspaper reporter, but they might get a job selling ad placements for that newspaper.)
--Depending on your school, the guidance office might have a subscription to a careers website (e.g. MyRoad or ACT's DISCOVER).