palmtop is a fault proof program that runs the rollup state transition to verify an L2 output from L1 inputs.
The verifiable L2 output can then be used to resolve a disputed output on L1.
The program is designed such that it can be run in a deterministic way such that two invocations with the same input data wil result in not only the same output, but the same program execution trace. This allows it to be run in an on-chain VM as part of the dispute resolution process.
palmtop is a computer small enough to be held in your hand.
In the 1990s, the palmtop PC was the elite mobile device equipt with a tiny keyboard and little smart pen. Until the iPhone.
In essence, this is the palmtop, and zk proofs will (likely) be the iPhone.