Offer-When production tells you (or more likely your agent) what they will pay you for which days and your billing and any other terms or conditions like your dressing room situation
Booking or Booked-When you have been offered the job and accepted
Closing-When your agent confirms your acceptance of the terms of the job and you are definitely set to do the shoot
On Avail or Availed-When they want you to hold the shoot dates because you are one of the two or three choices that producers are considering (primarily used for commercial work)
Pinned-Same as on avail but for theatrical work
First Right of Refusal-When production wants dibs, so you don't accept another job without giving their production an opportunity to offer you their job
Pocketed, Hip Pocketed, Back Pocket Client-When an agent or manager will work with an actor without signing a contract to "see how it goes" (I don't do this ever because I'm a lawyer, and I'd be the world's worst lawyer if I didn't get contracts, but lots and lots of other agents do)
SAG contract-The contract used by SAG and ATA franchised agencies. These contracts are the result of collective bargaining by the union. Not a single word on these contracts can be altered or removed. Don't ask. It can't be done. That's what a union does. They agree on a contract for you. Even if you aren't SAG, if your agent is, that's the contract they have to use. You have the right to check your contract out with a lawyer. It is available on the SAG website to look at in advance, but they can't change a word of it, so save your money unless your agency doesn't use the standard SAG forms.