Ok so what is a .CETRAINER file? CETRAINER files are automatic cheat tables, supported from Cheat Engine 6.1 and above. They are not stand-alone trainers, so you need to install CE 6.1 or higher in order to use them.

You can download CE from:
http://www.cheatengine.org

How do you use it?
If you have installed Cheat Engine 6.1 or any higher version, you can simply click on the CETRAINER file and the trainer will start up. It will look like any other trainer, the difference is that it is using Cheat Engine to do every stuff. It is very similar to a cheat table, when you enable a cheat, CE will do the job, execute the script as usual. The difference is in the user interface only. It looks like a trainer, you don't need to attach CE to the game as it is done automatically and the hotkeys are also set up for you already.

What is the advantage of using CE trainer over a stand-alone trainer?
1. It is very small in size.
2. You can easily see the source, so you don't have to fear from viruses and so on. Completely safe.
3. Just as easy to use as a normal trainer. There is no difference at all, except that you need to install CE for it.