Phazing is where you beatmatch two identical records together at the same time in the same place on each record, then you slow the pitch down just a tiny bit and it creates a whooshing sound effect as a result of the identical soundwave suddenly becoming dissimilar. It only last for a few seconds (if that) so you need to juggle the pitch up and down a fraction every couple of seconds. Although nowadays with built in effects in mixers and plugin units like the Kaoss pad, there's no need for it IMO.
What Mesh is on about is Phasing, two identical records beatmatched but playing in 1/4, 1/2 or a whole bar difference, so that you can play with the crossfader and juggle between the records, creating chopped up versions of said record being played. DJ Hype is well known for doing this to Planet Dust
Very easy to confuse the two