What are those tubes hanging down from the bike for?

There are a variety of tubes that are bound together at the bottom of the bike. These can include fuel tank overflow, coolant system overflow, carb drainage, and battery vent. These hoses are usually a little longer than necessary when you first get the bike; you can trim them a few inches if you like, but be sure to leave enough slack above the lower routing bracket, and a few centimeters of travel beneath.