Posture for Prayer

When we pray, does it make any difference whether we kneel, sit, or stand? Why do we close our eyes when we pray? We usually fold our hands and bow our heads? Is this "custom" or does it mean something? All of this is included in the posture for prayer. When we pray, does it make any difference whether we kneel, sit, or stand? Why do we close our eyes when we pray? We usually fold our hands and bow our heads? Is this "custom" or does it mean something? All of this is included in the posture...