One way to subdivide a tech startup is between product (technology, engineering, design) and business (marketing, sales, finance). Or perhaps more bluntly: the hackers and the suits.
The way I like to classify these two major areas of function is: creating value vs. capturing value. Another one is problem finders and problem solvers.
Eric Ries puts it like this:
Modern startups should only have two departments: the problem team (people in contact with customers and prospective customers, understanding and learning from their needs) and the solutions team (engineers designing and building solutions to those problems).