These are pretty much what they say they are, though around these parts they're more commonly referred to as Bike Pogies. For those who are unfamiliar they're used either to add an extra layer of warmth to your existing set up (we assume you already have warm gloves or mitts for winter cycling) or they can be used in place of warm gloves in milder temperatures. Instead you can wear 'regular' bike gloves underneath and therefore have a better grip on your bars and better access to your brake and shift levers, because the pogies fit overtop of the bar and levers themselves, creating a nice little pouch for your hands.
They're also really nice to use with small gloves because you can easily take your hands out of the pogies and with just a small glove remaining it's easier to fiddle with buckles, zippers, find loose change, fasten your lock, etc.
These pogies are made to work with either drop bars or flat bars, so they should work with just about any set up. If you're not sure if they'll work for you bring your bike down to the shop and we'll see if they fit. Worst case scenario, it's an excuse to ride down to the shop. Best case scenario, you buy them and they end up saving your fingers from falling off in our notoriously cold winter - don't be fooled, it's coming :)