It is rare to find complete beginners in the classroom. Almost everyone has had some exposure to English - however minor - and knows at least a few common English words:
...to name but a few. And most cultures have had a much greater exposure to English either through television or music.
Beginners should not be confused with age. You can find a class of beginners who are very young children and likewise a class of beginners who are mature adults.
False Beginners are students who have had perhaps some exposure to English and have a very limited grasp of the basics. They have either learned English many years before (perhaps at school) and are coming back to the classroom later in life, or perhaps they have had some contact with English speakers but no formal training.
False Beginners often learn faster than complete beginners. On the other hand, False Beginners may well have imperfect English embedded in their minds and this can take some work to correct.