Liquorice Lock is the first blocker introduced in Candy Crush Jelly Saga. Its first appearance is in first episode, at level 2. The blocker looks like a locked door, with liquorice surrounding the outside of the square and an X-formation.
Any kind of candies or swirls can be captured by a liquorice locked, and they can't move until they get unlocked. Locked candies retain their original properties except for mobility. However, the locked liquorice swirls have no resistance to special candies' effect.
How to let liquorice lock disappear? It depends what kind of candies or blockers. Special candies or their combinations are always effective to liquorice locks. Because other properties of locked candies or blockers are retained, you can also unlock them according to their properties.
For the list of levels with this blocker, see here.