Something that is flexible is easily bent without breaking. The flexible drinking straw was invented in the 1930s by a man who saw his daughter struggling to drink a milkshake with a straight paper straw.
The word flexible can refer to bendable physical objects or to intangibles like a person's mind, which can be changed. It can even refer to work environments that can adapt schedules and benefits to fit a worker's individual needs. Being physically flexible usually means good health, with no pain in movement. In all, it's great to be flexible, to be able to bend without breaking and bounce back, ready to keep going.