Web hosting is a service based on renting someone else's server. Specifically, you rent a small amount of space on the server's disk, and your website's files are stored there.
A website could therefore be run on your laptop, office PC or tablet.
Use
The most important requirement a server must meet is that it must be running all the time and have enough computing power to process scripts and the requests users make. The speed of the internet connection is just as important for fast communication.
All this is provided by powerful servers, which are placed in huge rooms, halls or entire buildings with the necessary cooling, connectivity and staff. The files on the server are usually accessed with clients that work over the FTP protocol.
In reality it would be foolish to use one server for one website, because a single website would not use the whole capacity of the computer. So it usually works like this: for a fee, a customer is rented part of a server, and several websites then run on one server. These websites do not “know” about each other in any way and cannot affect one another. The only thing they share is the server's performance.