Knowing the difference between cover and concealment when under attack is of vital importance. Cover is anything that provides varying degrees of protection from gunfire. Examples are brick walls, concrete walls, engine compartments of vehicles, logs, thick tree trunks, trenches, rock formations, a freezer full of frozen food items, hillsides, metal dumpsters, sandbags at least 12 inches thick, 55 gallon drums filled with sand, steel doors, concrete parking barriers and telephone poles. If it can stop a bullet it is considered cover.
Concealment provides a place to hide but will not stop gunfire. Examples are walls of a normal wood frame house, small trees, foliage, darkness, bushes, tall grass, shadows, car bodies, behind non steel doors, tables and couches. If it cannot stop a bullet it is considered concealment. Make sure you know the difference; it just might save your life someday.