Websites hosted on a server that share resources with other websites are virtual websites.
This is in contrast to a single machine dedicated to processing HTTP requests for a one website. Websites that are on the same server will have common resources to share.
Each site has its own partition on the server, however, keeping it separate from the other sites.
Typically, this is the most economical option for web hosting since many people share the overall cost of server maintence.
This is sometimes called shared web hosting.