I found a really really good, simple to understand website that describes the various printing techniques employed:
http://glossary.ippaper.com/default.asp?req=knowledge/article/151 (for flexography) and from this I learnt that:
Flexography is a modern version of litho printing... it uses rubber plates as opposed to metal, and therefore has a greater number of applications, such as: foils, plastics, paper and various types of food packaging (this is because food packing is usually required to be non-porous, and flexographic printing doesn't require the ink to be absorbed into the printing material, rather, it sits on top of it). Flexography is also used to produce some wallpapers.
The process uses raised image plates (the image itself is on the raised part... the non image is ... like... flat).... the image on the printing plate is in reverse, which allows it to be printed directly to the print surface, and not onto another roller in order to reverse it so that it's the correct way round.... if this makes sense). The printing roller is supplied with a certain amount of ink (specific to that image) on a roller called an anilox roller. The ink is very fluid, more often-than-not water-based and quick drying.
