There are many web development companies out there. There are even freelancers doing this on a part time basis. While the later might cost a lot less, the level of support you get may vary greatly. For one, you many never be able to locate that free lancer again. You would then have to approach another company for assistance on modifications or changes.
2 main ones are either informative or e-commerce. Informative is more of letting everyone know who you are, the services you offer and a contact page. E-Commerce sites are more complex as these are usually shopping sites.
Informative websites are usually stagnant and seldom change, unlike e-commerce websites which require constant updates.
Getting all the information ready can be a time consuming and daunting task. There is always the worry of leaking out too much. A good web development company will be able to guide you through this process.
Having a website designed, hosted, promoted and maintained requires the services of professionals from different fields. Most companies only offer one or the other. Choosing one which is able to handle everything is usually a better choice.
For example getting a website designed with one company and hosted with another may run into problems and when it does, both the designer and web host will be pointing fingers at each other. E-Commerce Services is an all round company which offers full range of web services.