Dream Theatre's keyboardist Jordan Rudess doing a demonstration showcasing the capabilities of the Kurzweil K2600 synthesiser which he used to bring on tour - he uses a Korg Oasys now.
A 'sampler' (which he mentions) is a device that enables one to record and digitised the sound of a live instrument, so that the sound of this instrument can be produced the synthesiser. It's a bit like the concept of a computer font on a word processor.
Joker who spends his free time milling around NUS pretending to be a student...