The E's

Under EU law, E numbers, or what I call "the e's", are the codes used to identify the food additives in Europe.
You find these on food labels over here.  It can be hard enough reading an ingredient label in English.
Forget about trying to figure out Czech, Danish, Lithuanian, or Finnish.  So the e's make it way easier to understand.  All of the e's are broken down to the following groups.

E100 - 199  = Colours
E200 - 299 = Preservatives
E300 - 399 = Antioxidants & acidity regulators
E400 - 499 = Thickeners, stabilisers & emulsifiers
E500 - 599 = pH regulators & anti-caking agents
E600 - 699 = Flavour enhancers
E700 - 799 = Antibiotics
E900 - 999 = Miscellaneous
E1100 - 1599 = Additional chemicals that do not fall into standard classification schemes

Taking this Dutch mayonnaise label as an example.

E270 = Lactic acid (preservative)
E330 = Citric acid
E202 = Potassium sorbate
E160a = Alpha-carotene, Beta-carotene, Gamma-carotene (yellow-orange to brown)
E385 = Calcium disodium ethylene diamine tetraacetate

The European Food Safety Authority sets the rules on food additives, definitions, conditions of use, labelling and procedures in Regulation EC 133 / 2008.