Flexibility refers to the range of motion at a joint; synovial joints like the shoulder provide high flexibility, whereas fibrous or cartilaginous structures offer more stability.
Flexibility relates to the range of motion available at a joint. It's a measure of how far and how easily one can move the joints within the limits of the joint's structure. Different types of joints provide different levels of mobility. Synovial joints, for example, are highly mobile because they are filled with a lubricating fluid that allows the bones to move smoothly against each other.
This is opposed to fibrous or cartilaginous joints which offer reduced mobility for the sake of stability. The shoulder joint is known to allow a great range of motion due to its ball-and-socket structure, whereas the carpal bones in the wrist, despite their complexity, provide a different type of stability.