Most hosting providers use one and the same web-server to simultaneously host websites of many of their clients. This type of hosting service if generally known as shared hosting. The most significant and probably the only advantage of this type of hosting is discounted price. Another side of the medal is that you will have to accept some inconveniences such as bandwidth, disk space and upload/download speed limitations, lower security and privacy level and absence of total control over the software and hardware used to host your website.
Total control over the hardware and software used for hosting is provided by the so-called dedicated hosting providers. This type of hosting is suitable for businesses large enough or growing fast enough to require a web-server of their own fully controllable at all levels.