In simple words…
Its a service provided by a company that allows you keep your website accessible 24×7 around the world (World Wide Web).
What about Web Hosting plans?
They are like your everyday bank services. You have a range of plans to choose from like a savings account, normal cheque account and so on. Likewise, Web Hosting plans have different limits such as how many website files you can store or how many visitors your account can handle every month (bandwidth). There is no ideal plan for all the websites since each website has different demands.
What about Shared, Dedicated, Virtual Private Server (VPS)?
Shared hosting is one type of service just like your bank accounts. You can have a personal account or business account. Likewise, there is shared hosting account and a dedicated hosting account.
Shared hosting is basically sharing a computer that is switched on 24×7 (see above) with other people who want to host their website files with yours.
Dedicated hosting on the other hand is quite opposite. Its being able to host your websites files on a computer specially kept just for you. In this way, other website’s load will not impact your capacity and all the computer’s resources such as its memory, can be used just for your website.
Virtual private server fall in between these both accounts by allowing you to host your websites on computer shared by other but restricting excess usage from other websites. So the resources given to you will be only yours to use.