RDP stands for remote desktop protocol. It is a technology developed by Microsoft which enables users to connect two computers remotely. In simple words it lets two computers at two different locations to connect with each other over the network through internet.
Let's take a simple example, suppose you stay in india and your friend stays in UK and for some reason you want to use his computer but you don't know how to do it, here is when RDP comes into play, you can access the computer of your friend sitting anywhere in the world by using RDP. It allows printer sharing, sound sharing and a host of other features.
Another important use of RDP is that you can use it for any problem solving activity by sharing your computer with the technicians etc, in this aspect it works in the same way as team viewer. Another use is that lets suppose your PC is not in a good condition and you are not happy with the configuration and you have a friend you lives in Germany and has access to a good configured PC, so by using RDP you can access your friends PC by sitting in India. Isn't it amazing?
For using RDP all you need is an IP, password and a computer name which will be provided to you by any RDP service seller. There are many RDP providers in the world and you can choose them as per your needs and the configurations they provide. The RDP provider will you the details by which you can use RDP on your computer.
Now apart from people looking for high speed internet, hackers also use RDP to stay anonymous and use faster internet. The role of RDP provider is very important here because it's the provider who will make sure that the users does misuse the service for unethical activities like child pornography, hacking, gambling etc.
In this age where most of the internet activities are performed on phone, RDP is not different, you can access RDP on your phone by installing a bunch of apps for android and iPhone users and you don't need to fear for your security as well when you use RDP because it is encrypted by 128 bit by Microsoft which makes it super secure for use.
In the end I would just like to say that RDP is an extremely useful service provided that users use it for ethical and legal purposes and choose their provider intelligently.