The Common European Framework of Reference for Languages: Learning, Teaching, Assessment, or CEF (also CEFR), is a standard guideline used to describe achievements of learners of foreign languages across Europe. 

It was put together by the Council of Europe as the main part of the project "Language Learning for European Citizenship" between 1989 and 1996. It has been incorporated into the European Union's Europass, which contains the European CV and the Language Passport, and can be used by job applicants to indicate their language proficiency.

The main aim of the framework is to provide a method of assessing and teaching which applies to all languages in Europe. In November 2001, a European Union Council Resolution recommended using the CEFR to set up systems of validation of language ability.  It has been translated into 35 languages (including non-European languages such as Japanese and Arabic).

The CEF describes what a learner is supposed to be able to do in reading, listening, speaking and writing at each level, in details:

If you would like to download my coloured version of this in .pdf format, click here . 

The six reference levels (A1 - C2) are widely accepted as the standard for grading an individual's language proficiency.  Nonetheless, existing examination boards and publishing houses have retained their own naming conventions, e.g. "Intermediate", which are, arguably, easier for them and students to remember.

However because these names are so subjective, across nations, institutes and books, SimplyConversations^TM only uses the CEF.  Each prompt sheet carries a reference link at the top of the page which indicates the lowest language level the cards can be used with.

For a cross reference to what this means according to your own/your institute's system of evaluating levels (or to compare against ALTE) see wikipedia's Common European_Framework_of_Reference for Languages or ask your Director of Studies.