What's the difference between wet lube and dry lube?

Search online or visit a big bike shop and you'll be confronted with a bewildering variety of chain lubricants. However, they can can all divided into two types: "Wet" and "Dry".

Wet chain lubes are a similar technology to car motor oils. They aren't easily washed off in wet riding conditions. They stay wet on the chain which has the disadvantage of picking up grit and dust that can make the chain wear quicker. 

Dry lubes use a completely different technology: suspending wax in a solvent. When applied the the chain the solvent helps the wax get between the bearings before evaporating and leaving the chain nice and clean and non-oily. Disadvantages of dry lubes is that you need to apply it more often than wet lubes and they can wash off very quickly in wet conditions.