You need :

a web address = DOMAIN NAME

a place for your website to “sit” where the website domain name is linked to = WEB HOSTING

to build a website = WEBSITE DESIGN OPTIONS

You may need:

a secure encryption for online shop transactions or database connections = SSL CERTIFICATES & SECURITY

systems that use information that are stored in a database (customers/shops) = SERVER SIDE TECHNOLOGY eg. PHP, COLDFUSION, ASP etc

credit card facitilities unless you want to use Paypal for credit cards = CONTACT YOUR BANK

Important extras:

having your website turn up in popular search engines = SEARCH ENGINE MUST'S (SEARCH ENGINE OPTIMISATION)