digital / wordclock .... in order to understand what they do and how a better or worse clock can influence your audio you need to understand what jitter is.
There's a great technical explanation on jitter by Bob Katz at Digido :
http://www.digido.com/portal/pmodule...er_page_id=28/
more specific to your question :
Jitter occurs or can be added whenever your digital signal goes through a conversion ... A/D or D/A. A proper clock basically prevents time errors by making sure that all devices in your digital setup synchronise their digital data to this one clock.
typically a better or worse clock will result in things like :
- better or worse stereo image
- tight or less tight low end
- loss of depth / dynamics in your sound