Hello,
I am starting a new automation project in my home and I want to choose some items to start working with.
My problem is that I have no idea about items that can be used.
Is there a way to get a description for each supported item ? What methodlogy should I follow?
Thx 
Start with the getting started page.
Think about downloading and installing the demo files (further down on the getting started page).
Items (and everything else) are explained in the wiki. (and here is the items section)
Have fun.
You could start by using the weather and/or systeminfo bindings, so you get the look and feel of openhab. Then it really depends on what you want to automate (lights, sensors etc) and the associated bindings. That will get you the feel of what items are and what you can do with them.
Thx guys. And Shoul I start with the 1.8 version or the 2.0?
Start with 1.8. Iād only recommend OH 2 to those who are already familiar with OH 1. OH 2 does not have complete documentation yet and OH 2 is still in beta and undergoing a lot of development which can trip up new users.