Mindful range of motion
Range of motion is the amount you can move your joints, or the angle you can make with your joints. A joint is the connection of one (or more) bones and depending on the shape of the joint and how muscles and ligaments attach to that joint, this will determine a natural range of motion for that joint.
For example, the shoulder joint is a ball and socket joint. Imagine a ball inside a cup, that's the shape of your shoulder joint, and as a consequence of the shape of the joint your arm can move in many different directions inside that shoulder socket. It can move, forward, backwards, up and down and around in a circle. Another example of a ball and socket shaped joint is the hip joint, where the upper leg bone meets the pelvis. However, this ball and socket joint is deeper than that of the shoulder so there is less range of motion in this joint. Your leg can move forward, but not so far backwards. It can move out away from the body and back in, but your leg can't do circles like your arm in the shoulder joint can.
As a final example, think of your knee joint. This joint connects the upper and lower leg bones and it is a hinge joint because, much like a door hinge, the range of motion is only in one plane. The knee bends and straightens but it doesn't go side to side. So you can see there are different planes and possible movements each joint can perform and this is the natural or range of motion for a particular joint.
Personal range of motion
So now the question is, what is your personal range of motion? Well, for example your personal range of motion in your shoulder joint will be similar to, but not exactly the same as another person's. This will differ slightly because we all have unique and slightly differently shaped bones and joints, but most commonly your range of motion will be determined by muscular length and flexibility. Understanding and knowing your own personal range of motion will help you make better movement choices in exercise and other physical activities.
Mindful range of motion
So how do you determine what your range of motion is. I say this in particular reference to pushing into a stretch vs relaxing into a stretch. For example, when you sit upright on the floor, how far can you bend forward comfortably. If you bend forward to a place which feels comfortable, where you can stay in that position without feeling pain, then you have found your personal range of motion for that movement. You can always push your body past this point, but you will notice pain and stretching. Now, there's nothing wrong with that, if that is your aim, however I'm writing here to help you become aware of what is comfortable for the body and what is not and the benefits of finding this point and not pushing beyond it into pain. Pain creates tension in the body, as it naturally wants to pull away from pain. In the classes I teach here I encourage you to stay out of pain and in curiosity of what feels good.
On finding the edge of your personal range of motion you will be able to explore where you hold tension, how you move, your personal flexibility at this point in time without the body reacting against pain and strain, which is what would happen when you push past this edge. That is why I'm calling the is a mindful range of motion, because as you do this you are bringing your awareness to how your body feels in a posture or shape and you will be able to explore and change from there, helping you open up to find more expansion and to feel good.