They are formed when snow falls on the already icy land on the shores of the Antarctic continent. The snow never melts and eventually there is so much it begins to pack down and form ice. That ice eventually begins sliding into the sea - thus, an iceberg is born. Most icebergs display only 10% of their total mass above water while the other 90% remains beneath the surface. It takes hundreds and thousands of years for an iceberg to form to the sizes we usually see.
