With a website, you can offer your customer this very important resource. You can set up a few pages covering FAQ's. FAQ's are frequently asked questions. Post these along with the answers and you have just given your product or service powerful support. Customers now have the answers to many of their questions at their finger tips.
Email is a very powerful tool.
A customer may leave you a question via email. You now have time to research the answer and then reply to the return address. You can send updates and pictures to support your products or services via email. You can set up pages for customers to download software. Internet access is now very affordable.