ok, ive searched and haven't really found my answer.

What do the numbers for the gear ratios mean?

for example, the bike im looking at is a DK Rage, which has a ratio of...39/14

What does the 39 do and what does the 14 do? (i know the 39 is the chainwheel and 14 is freewheel)

What happens if you raise/lower these numbers in various combinations?