掩 is a literary/formal verb with three main strands: physically covering something (often with your hand or a cloth), concealing something abstract (like emotions or identity), and shutting a door or book politely. It also appears in military phrases like 掩杀 (ambush) and in some dialects means 'to pinch' (手被门掩了). In everyday speech, 盖 or 关 are more common; 掩 gives a more refined or written feel.