La bise is the kiss-kiss (one on each cheek, usually) that the French are known to use when saying hello and goodbye to one another. In some regions, it is customary to do three kisses or four kisses, which can be really confusing for a non-French person to figure out.  But after a while, you will get the hang of it.

For more information on La bise, watch this thoroughly entertaining clip by comedian Paul Taylor.