I don't know its equivalent in the Greek system, but I can speak about it from a general perspective, and perhaps that will help you figure it out in terms of your system.
In England, they determine the class of your degree based on the average marks you've obtained in your work (your average grades). Undergraduate degrees are awarded as follows:
* First-Class Honours (First or 1st)
* Upper Second-Class Honours (2:1)
* Lower Second-Class Honours (2:2)
* Third-Class Honours (Third or 3rd)
* Ordinary degree (Pass)
* Fail (no degree is awarded)
When British universities talk about wanting you to have a 2.1 or a 2.2 honours degree in order to apply to their MSc programmes, they mean that you need to have a bachelor's degree from a reputable university with grades that are the rough equivalent of, using the US system as a point of reference:
- a 3.5 or 3.75 out of 4.0 possible points for the 2.1 degree, or
- about a 3.0 or 3.3 out of 4.0 possible points for a 2.2 degree.