Having a dedicated server gives you high flexibility and a lot of options for your site. You have root/admin access to the server and you can manage and modify each aspect of the server behaviour - software running, configuration, etc. So if your site needs more than any shared hosting plan can offer or if you have some special requirements then the dedicated server is the right choice for you. When you are on a dedicated server your site is the only one that uses the server resources. Also when on a dedicated server you have no restrictions on the number of websites that you can host, or on the number of mailboxes. The whole CPU and memory is on your disposal. You can install whatever programs and software that you wish.