The Merriam-Webster dictionary defines posture as “the position or bearing of the body whether characteristic or assumed for a special purpose”. Understanding posture will improve your ability to fit and pattern garments as posture affects the shape and movement of a garment (two of the four keys to good fit).
It is helpful, therefore, to notice the posture of your customer.
What is the characteristic posture of your target customer? This is a posture she defaults to when standing or sitting naturally. It could be due to things like her build, age, height, habits, bust size, level of fitness, etc.
What are the assumed postures of your target customer? These could be postures deliberately taken on for work, motherhood, wearing heels, posing for photos, etc. They aren’t the person’s relaxed posture, but ones she consciously takes on because she wants or feels the need to.
Once you understand the common postures of your customers, you can translate that into the fit of the styles you develop. Your customers will feel like the garment is made just for them, because, in a way, it is.