Simply put, fitness means "biopsychosocial-spiritual well-being".

The origin of the word comes from English, where fit means "good shape" and ness is simply a suffix that gives the word the value of condition/state.

When we refer to fitness we speak of the potential for performance as a function of genetics, and when we refer to conditioning we speak of physical performance and development as a consequence of training.

Thus, physical fitness will influence physical conditioning to the extent that an organism presents greater or lesser efficiency in all daily activities, such as sitting, standing, running, walking, endurance, and resistance to certain movements and positions, as a result of personalized training.

For example, a person may have genetics (or, as the jargon goes, a "knack") for running, but if he never runs (that is, has no physical conditioning for the sport) he will not develop this potentiality.

To conclude, being fit is not just havi ng good physical fitness or good physical conditioning, it is eating healthily, having a positive social life, training effectively to keep the body active and alert to respond to any emergency, being able to meet your needs on your own, being resilient and adapting to your changing environment, and being able to tie your shoes when you are old.