Websites tend to fall into one of three categories: Web Presence, Web Store or Web Application.
Web Presence
The goal of these sites is to inform internet users about your business and to present your services. Usually just a collection of simple pages, when properly created these websites make it easier for customers to find you.
Web Store
Designed to sell a product to customers around the country, these websites need to present your products in an easily searchable and secure environment. These websites also contain quite a few tools that allow you to organize and present your products, as well as to fill the orders submitted to your store.
Web Application
In today's distributed business environment, many companies need a place on the internet where users from around the country, or even the world, to enter and view corporate information. A well-written web application allows users with any web browser to quickly and easily access the information they need to use to accomplish daily tasks.