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.