Ambient is the title of the secret track on the Hybrid Theory EP. A.06 was an unfinished song that Linkin Park used a lot to advertise Meteora(when it first came out). If you remember the commercial with the people riding four wheelers...A.06 was played during that commercial.
there is a simillarity, but session is better in my oppinion ambient doesnt have the scratching that session has but i see wot u mean