What is oral-aboral axis?

Answer 1

termed the oral, or anterior, end, and the other of which, called the aboral, or posterior, end, forms the rear end of the animal and may bear the anus. The main axis is hence termed the oral-aboral, or anteroposterior, axis. Except in animals having an odd number of parts arranged in circular fashion (as in the five-armed starfishes), any plane passing through this axis will divide

Or basically if you want to look at it, oral means cutting the organism horizontally and aboral means cutting the organism vertically.