Dental: the hygienist said that a sulcus is different from a pocket. in layman's terms, how are they different?

Depth,problem: A pocket can be thought of as a sulcus gone bad. The sulcus is the "moat around the tooth", kind of like a turtleneck. We measure the depth before we feel resistance which indicates where the gum attaches to the tooth. If this is about 3 -4 mm or less, then it is considered cleansable by you. If greater, then considered a pocket, and not maintainable by you. Potentially a problem.

Sulcus v pocket: Sulcus is the space between the free gingiva and the tooth aprox 1-3 mm. The depth of a periodontal pocket is greater than 3 mm. A pocket deeper than 4 millimeters indicates that you have gum disease.