What is the difference between chosen-plaintext attack and adaptive-chosen-plaintext attack?
With chosen-plaintext attack, the attacker is allowed to choose an arbitary amount of plaintext to encrypt. After that he/she can't do that again, he/she has to work with the current data.

With the adaptive-chosen-plaintext attack, he/she can do the same as with the chosen-plaintext attack, but is also allowed to encrypt new data after the attacker has looked and analyzed previous encrypted bits. He/she can, based on the already encrypted data, choose new data to further advance his/her attack.