Fascia is the tough connective tissue that creates a 3-dimensional web extending without interruption from head to toe. Fascia surrounds and infuses every muscle, bone, nerve, blood vessel, and organ, all the way down to the cellular level.
Have you ever head of Proprioception? It's a big word that basically describes how you can feel where you are in space and time. You can test your proprioception with a simple task: close your eyes then touch your nose. You don’t need to look to know where the position of your nose is in space and how to bend your arms.
In the mainstream, we are taught to think of the body almost as a brick wall or a house with everything stacked on each other. In early human cadaver research, researchers only knew muscle, bone, organs, etc. Fascia and connective tissue was tossed out as it got in the way. Researchers assumed it was just stuffing and had no actual function. So in normal education, the human body is just thought of as a skeleton with muscles.
The human body's ability to mold to the stresses applied upon it is one of our biggest strengths. Your body's ability to remodel tissue in response to activity is largely explained by the viscoelastic properties of fascia.
Previously muscle was the be all and end all of sports performance. How much force can your muscles produce? How much strength can your muscles exude? How big are your muscles? How fast can your muscles contract? How many fast-twitch muscle fibers do you have? Etc, Etc...