Explaining jitter would take several pages, so the best you can do, if you really want to understand what it is, is read articles on the net.
For DVDRs and CDRs, you can picture "jitter" as a relative deviation of the "pits and lands" from their ideal location, shape and/or lenght. This is definitly not a really correct explanation, but it's sufficient for the purpose of understanding why jitter is a concern with optical media.
Standards limit acceptable jitter to 9% (DVDR), but the problem is, you don't know exactly what the drives report (Benq, Plextor and LiteOn) and if the values are reported in a way that is compliant with the standards, so you can't really rely on these standards to appreciate your burns.
There are questions, though, about the Benq's jitter reporting, as some discs showing very high jitter in these drives don't show such high jitter in other testing drives. This is a complex and controvesial subject, just as PIE/PIF scanning relevance. :doh: (probably even more so :bigsmile: ).
I only have experience with Benq jitter reporting. I've come to consider (from cross-checking behaviour in other drives/players) that jitter levels reported > 10% (in @8X Benq scans) are an indication of a lesser burn or media, as such discs are less widely compatible with full 16X reading in several drives (some of my drives show a slowdown near the end with such discs if the > 10% jitter is reported in this area). But that's my book, from my own experience with my own discs and hardware.
The can of worms is opened. Bring it on. :bigsmile: