Shared hosting is a form of web hosting in which many web hosting customers share a single (virtual or physical) server.
The customers in a shared hosting environment are partitioned away form each other, so (when everything goes well), they have absolutely no access to each other’s files, and are ideally not even aware of each other.
Shared hosting allows for a high customer-to-hardware density, which makes it a very inexpensive way to run a website — shared hosting is the cheapest form of hosting, and relatively high-quality shared hosting plans can be had for less than $10/month (sometimes less than $5/month, with a good coupon).
The problem with shared hosting is that a limited pool of computer resources is being shared by a large number of customers. This can cause slow-downs and site outages if one or more sites on a shared hosting server gets a lot a of traffic.
To prevent this, shared hosting providers usually institute some kind of throttling — even on so-called “unlimited plans.” This usually kicks in if your traffic spikes, which makes shared hosting plans a terrible idea if you are trying to build a highly-scalable, well-trafficked website.
