Se1 Episode 1 – The Boy in the Iceberg

During Katara and her brother was at a mission at sea, they saw a boy named Aang in an iceberg. Aang is an airbender nomad whom all thought that such people are extinct. Katara made friends with Aang and give him a warm welcome. Sokka is more hesitant but he just join along. Who is this Aang? Is there something secret that he knows which others don’t?