When we're talking about ethics, we're discussing standards of behavior. Those standards can be set by a company, an individual, a society, or other entity - while hopefully evolving and improving as time goes on. But being able to call oneself an ethical person ultimately comes down to an individual's ability to live an ethical life.
While there may be some debate as to what isn't and isn't ethical (a debate perhaps best left up to the philosophers and social scientists) there seems to be a positive correlation between being ethical and a greater well-being. And while there are exceptions - there are scumbags living comfortable lives and saints struggling to make ends meet - ethics can have a tremendous effect on you and your future.
In business your ethics have a direct impact on your customers. While some customers may not care that your products come from sweat shops or that you don't pay your taxes or that you rip the tags off of mattresses, they will care if you have shoddy products, use deceptive marketing, or provide lousy customer service. In decades past the occasionally dissatisfied customer may not have been too big of a problem - at least not enough to improve your practices - but the Internet and its complaints boards can turn one incident into a business killer.
Your behavior will also affect your interactions with other businesses. You may have clients, distributors, or other organizations which will base their desire to work with you on the kind of relationship you have and reputation you've built. A surefire way to damage that reputation and hamper those relationships is to engage in unethical behavior.
Instituting and encouraging proper ethics is more than just establishing a set of rules for people to obey or protocol for people to follow. Doing that on encourages people to find the loopholes and the gray area they need to do what they want to do. While it's okay to have guidelines, establishing a proper ethical environment requires encouraging a culture of ethics. And whether you're the CEO, manager, or intern, the ultimate responsibility to be ethical is up to you.
There isn't much of a difference between personal ethics and business ethics. People can try to say their personal life and behavior doesn't affect their professional life and behavior, but it does. The little indiscretions and rule bending you do in your professional life will affect your ability to be ethical in your personal life, and vice versa.