Actually the word promoter is used for many people. Its prime use is in business, Where a Promoter refers to a person who owns a business or has close personal interest in it. Normally people who have a high stake in the business are known as promoters.
Promoters are very important for the business. They are not just the owners, they are the propagators of the business. They seek out possible investments and opportunities. They arrange for finances and seek out investment of retained earnings. They are important because they have the contacts to manage the business on their credibility.