Each of the properties you have listed, details information about the projection and who was responsible for the event being linked/emitted.
$v describes versioning information and is as follows:
$v = Projection id.
The $projections-$all stream is basically a registration stream which stores a list of events that tells the projection subsystem which projections are still alive and needs to be loaded on startup. You will see events such as $ProjectionDeleted, $ProjectionCreated in that stream. The projection id is the event number of the $ProjectionCreated event for this particular projection.
$v = Projectionepoch.
I can explain this a little more if you are interested.
$v = Projectionversion
Every time the projection is updated, this number is incremented.
$v = ProjectionSystem Version
Identifies the version of the projection sub system. Currently at version 3
$c = Commit Position
$p = Prepare Position