The web hosting (known also as ‘web host) is a business that provides the ‘necessary technologies’ and services needed for any website or web-page under a certain domain name to be viewed in the Internet by the entire world.
By ‘necessary technologies’ we understand a network made up of more machines (computers) know also as ‘web-servers’ located in a data-centers.
So, the websites are hosted (or uploded from your PC and stored, on those special computers called web-servers and that hosted website get connected to the Internet throgh the web-servers which is permanently switched ON and permanently connected to the Internet. Therefore, the hosted website consisting in all the folders and files is taking a space on that web-servers and that taken space it is called: web hosting space. It is the same as any file or folder is taking some space on the computer that can be a few Megabites or a few Gigabites.
This is how a web-servers or dedicated server looks like:
All the web-servers are kept in special racks in those modern state of art data-centers, all connected to the Internet permanently. The web-servers are running by using an operating system (O.S.) and other software that help for the machines (servers) maintenance and the administration of the web hosting accounts (client’s accounts).
This is how a data-center looks like: