What should I expect in the Computer Science field?

Computer science is (quite fortunately) a very broad and deep area of study, and can afford you opportunities in a broad number of fields. For example, I have leveraged my computer science degree in order to build a career in consumer software development (more specifically: web-based software development). A number of my friends have used their degrees to become quality assurance engineers, professors, network engineers, and entrepreneurs.

The most common work-related skill that will be required of a computer scientist is the ability to read, write, and manage quality code. The most common programming languages that I have encountered in my years as a web-focused software engineer are Java, PHP, Python, and Ruby; however, there are a vast number of additional languages in the various technical fields that are creating demand for competent developers that can specialize.

Since the majority of programming languages adhere to the same core principles of construction, it is rarely an insurmountable challenge to learn an additional programming language. My recommendation is to begin learning a language that is innately object-oriented and has a significant amount of developer assistance tools (such as Java). Once you begin to understand the nuances of how good code is structured, it will be easier to transfer those core skills to the learning of another language. All good university curriculums will focus the majority of your effort on learning these fundamentals (as opposed to simply teaching you the ins-and-outs of any specific language).

A bachelors of science in Computer Science is usually a breadth degree, so you take courses in a bunch of different fields of computer science such as OS, Networking, Databases, Artificial Intelligence, Compliers, Programming. From there you decide what interests you the most and you can decide to pursue a post bachelors degree in that specialization or you can join industry and use you skills.

I agree with Bryan's answer but would like to add that you should probably also have a solid background in Algorithms and Data Structures, no matter which particular career or which programming language you end up choosing.

First, a lot of basic algorithms and data structures are actually being used on a daily basis even in the coolest tech companies, and second, getting a solid understanding of these will help you develop a "computer science" way of thinking (how do you develop an algorithm to solve a particular problem? how do you tell if an algorithm is good? what are some of the limitations when developing computer programs? etc.). It is a lot about math in general, but then you also need to be able to translate your ideas efficiently into code.