snapshot compatibility list : Local vs. Shared Disk

Hello,

in the Snapshot Compatibility List (http://www.symantec.com/docs/TECH126901 ), there is a section "Disk". I see that it reports supported snapshot combinations which are independent on array vendor. But can somebody explain difference between Local and Shared Disk sections?

Because, for example, "Local Disk" section contains also Alternate Client methods, so the disk must also "Shared" in some way here.

Regadrs

Michal