The center of gravity of an object is a point at which all its weight can be considered to be located. This point is usually inside the object. However, your center of gravity may be inside or outside your body, depending on whether you’re standing, sitting, bending or falling over.
If your center of gravity is over your feet, then your remain upright. But if it is not above your feet, then you will fall over-unless, of course, you’ve taken the precaution of having a chair or stood under you.