Salt provides friction when you are crushing garlic or other ingredients with a mortar and pestle. Coarse sea salt is best, but regular table salt will do. When crushing mastic for use in sweets, a pinch of sugar serves the same purpose.
Dried herbs should be crushed between the fingers to release their fragrance before use; dill seed should be crushed thoroughly with a circular motion in a mortar until fragrant.
Many stews are finished off with a tiqlaya: Garlic or onion, fried crisp in plenty of extra virgin olive oil or butter, sometimes with other aromatics like coriander, and added at the very end of cooking to provide a bright jolt of flavor.