Your singing posture can mean a full, open voice or a tight and strained sound. Which singing sound do you produce? Evaluate your posture in front of a full-length mirror. Notice the way you hold your body, especially your head, chest, hips, knees, arms, and hands. More than likely, after you looked in the mirror, you changed your posture.
Did you change your posture because you thought your body may work better or because you thought you may look better? For singing, you evaluate your posture for both reasons. Aligning your body properly puts all the muscles that help you sing in the right position. Proper alignment gets you singing better and also makes you appear confident and professional.
Look at the following illustration and check out the alignment of the skeleton. Take some time to study the skeleton and notice the connection of bones.

As you continue to evaluate your own posture, notice the posture of others. Observe their movements to better understand what you need to do to change your own alignment.