The term is commonly used in the context of business and startups, where the founder is basically someone who founds and establishes a business or start-up. A co-founder is basically a person who helps the founder set up the company, and lends their skills or resources to the business and idea.For example, Bill Gates is the founder of Microsoft.Just as Bill Gates can be called a founder, he can also be referred to as a co-founder, since he co-founded Microsoft with Paul Allen.