you are looking at source media to destination sequence patching.
Left side represents the tracks available in whatever source is in your source viewer. enabling or disabling those means that when an edit (insert/overwrite) is performed, only those trax of material from source will be edited to the timeline
Right side represents tracks available in the sequence.
enabling and disabling those determines how those tracks will be effected by the insert or overwrite edit you are about to do.
so if you have material on multiple tracks in the sequence, and you do an insert edit with only some of the destination tracks highlighted…then only those tracks will ripple when the edit is performed.
same is true for overwrite – if not all sequence tracks hilighted…then only the tracks hilighted will be overwritten.
where there is no corresponding source to destination “patch” black is overwritten or inserted.
Alex Udell
Editing, Motion Graphics, and Visual FX