Licks are specific measure-long sequences of notes. (They can be even longer sometimes).
All the examples given above are officially "licks" but licks also tend to have a distinctive quality such as some special effects and an odd syncopation.
Here is probably the most important lick for bluegrass banjo playing:
Try it.
If you can play it smoothly, great.
If it looks confusing (as many licks do in tab), here is the way to break it down.
First, ignore all the left hand fingering and just find the basic roll and the open strings:
Then add in a single basic note (without special effects),
then add others,
then add one of the special effects.
Finally, add the other special effect (see the original roll above) and you've got it!
When doing this, play the roll 10 times through for each change and things will start to fall into place.
Here is one example of using various licks to spice up a song.
It is all regular roll until the end where some special effects are added.
Once you get it figured out, add more special effects to the early measures.
