In the UK it must say:
Glycerine, BP
or
Glycerine, EU
It must say exactly that on the label or it can be anything. Don't touch anything else as it won't be pharmaceutical grade, which is the only grade you should inhale. Other grades can have several per cent contaminants, it's not important for food because the digestive system can take care of it.
There are 4 grades:
Industrial Grade
Agricultural Grade
Food Grade
Pharmaceutical Grade [inhalation]
You can add from 5% to 20% distilled water to it, to thin it out. This is normal. In fact you must add at least 5% to it, for several reasons.
Of course, you can vape anything you like, but the only material advised for inhalation says 'Glycerine, BP' on the label. Other products are very likely to have a higher percentage of contaminants.