A colleague of mine stepped into my room today with this question.
For those of you entering the amazing world of print – not many these days – and having to deal with quotations from old-school professional printers and getting befuddled by it all, here is the clearest distinction, found on (actually surprisingly) a printer’s website.
In a nutshell:
Full colour printing involves mixing the four colours (CMYK) in the relevant amounts to produce a specific colour. Most useful in the printing of images.
Pantone colour printing is using a specific Pantone colour found from Pantone colour books. This is not considered a mixing of colours. Therefore, if your brochure contains only one Pantone colour (including percentages of it) and black, it is considered two colour printing. Most useful in corporate branding.
For a bit more detail, read here.