There are four main types of distribution channels: 1. Producer to Customer - the shortest channel without middlemen. 2. Producer to Retailer to Customer - involves one middleman, the retailer. 3. Producer to Wholesaler to Retailer to Customer - the most common channel with two middlemen. 4. Producer to Agent to Wholesaler to Retailer to Customer - the longest channel with three middlemen. The appropriate channel depends on factors like the product, market size and geography, and distribution costs.