Web hosting is a service which allocates space for customers to showcase their websites on computer servers that are connected to the Internet 24/7.
Servers are powerful computers that have extremely large hard drives, or an array of hard drives. Space is then rented to those who want a "website presence" on the Internet.
Every server on the Internet has a unique numerical IP (Internet Protocol) address. You can think of servers as apartment buildings with unique addresses. Each apartment unit within each building is equivocal to space rented out for individual websites. And like real apartment buildings, each unit also has an address based on "the building" in which it is located.