Corporate governance, esp. for small business

How does corporate governance work in a small- or micro-business environment? (Note: This post is somewhat US-centric, but I'm certainly interested in hearing perspectives from other nationalities/cultures as well!)

In a small, privately-owned business, how are the various corporate duties and responsibilities typically divided up?

As I understand it, there are basically three groups of corporate leadership:

Group 1:
- Chairman of the Board
- Director
- Director
- etc.

Group 2:
- President
- Vice President
- Treasurer
- Secretary
- etc.

Group 3:
- CEO
- COO
- CFO
- CTO
- CIO
- etc.

While I generally understand the where the Board of Directors fits in, I'm less clear on, say, the difference between a President and a CEO. One person can have both roles -- but what's the difference between the roles?

Similarly, what does the Treasurer do, exactly? How does that differ from, say, a CFO?

And apart from taking minutes and signing things occasionally, what exactly is a Secretary's role? Do they do other things as well?

I'm particularly interested in how these roles relate to the small-business environment. Is it "okay" for the same person to be Chairman, CEO, and President? When the time comes for the group of leadership to grow, which of those responsibilities should be given to someone else? If there are only 1-2 owners who actively run and participate in the business on a daily basis, is a board of directors even needed?

I've looked over Wikipedia, various business books, etc., and I can't seem to find a clear explanation of these relatively simple things. It's as if it's assumed that everyone already knows these things. I must have missed that day. :-)

(Sorry for the big batch of questions, but they're all basically about wanting to better understand corporate governance.)

Thanks!