Web hosting is a service that allows individuals and organizations to have a website made available via the World Wide Web. Web hosts are usually based out of a data center that contains servers used to store the data that makes up the client websites.
At the most basic level, clients upload their website files to the host server via File Transfer Protocol or a web interface that mimics FTP functions.
Web hosts may own their own servers or may simply rent servers from other web hosts and resell the space. Most web-hosting services are shared, meaning that multiple websites owned by different clients share space on the same server. Dedicated hosting is also available, in which the client rents an entire server for itself that it has full remote control over, but this is generally much more expensive than shared hosting. Managed hosting is a slightly less-expensive service that gives a client a dedicated server but only limited control over its function.
A relatively new form is cloud hosting, in which client data can be stored on multiple servers in different locations. This makes the hosting potentially more reliable, since it doesn't rely on one physical server, but it also potentially can increase the possibility of security breaches.