A dedicated server is a hardware machine operating 24/7/365 in our datacenters which you can use for hosting websites or anything else (such as virtualization, docker and so on).
The “dedicated” term is mainly used due to the fact that you are the only one which is using the server for your application. The only one with access to it to read/write data. So it is dedicated to you.
Unlike a VPS Server or VDS Server, which is running on a hardware server along other Virtual Servers, a Dedicated Server will be dedicated to you and you only.