Some of the most common MBA specializations are: Finance, Human Resources, Marketing, Operations and Systems Management. But then there are also a whole host of funky courses emerging in things like Football Management and Wine Management. It's really kinda ridiculous, and there'll probably be an MBA in setting up MBA programs before you know it!
A Finance specialization has a number of sub-specializations within it, such as: corporate finance, costing, investments and securities, budgeting, international finance, and working capital management. By covering a range of different topics you get some flexibility in the type of role you can take on, from working in a commercial bank, investment bank, securities firm, or even managing the finances of a company in a different sector.
This structure of offering sub-topics is typical of all the specializations. For example, the Human Resources specialization is divided between corporate personnel, plant personnel, and human resources strategy. Whatever specialization you chose in the end, the important thing is to keep an open mind on all the topics so that you have flexibility in your career path.