Answer:
What does everyone know how to open but not how to close?
Lovely and round, I shine with pale light, grown in the darkness, a lady's delight.
This is in a realm of true and in a realm false, but you experience me as you turn and toss.
Salty water everywhere but not sea in sight.
Soldiers line up spaced with pride. Two long rows lined side by side. One sole unit can decide, if the rows will unite or divide.
What covers its face with its hands, speaks no language, yet most known what it's saying?