A/D: track & hold?

These are essentially the same thing, especially as-used. The basic idea is that the signal to be sampled is applied to a capacitor through a switch, and when the switch is opened the capacitor retains the sample. (It's read out via a high-Z buffer amp that doesn't discharge the cap significantly in the sample times used.)

The T/H has the switch closed until the sample is required. The S/H closes the switch briefly to charge the cap, then opens it again. In practice, I'm not sure that you can depend upon the terms being used this way. I suspect that unless they are actually designing A/D chips or something, most folks would use S/H to mean "the circuit that grabs the sample" without worrying about the specific implementation. It's the specs that matter, like how well it can handle a voltage step and how much droop it has over time.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis