one way that you can represent it is for example if someone kick a soccerball.
ax^2+bx+c
ax^2 is a quadratic function which in this senario represents the balls downward movement.
bx is a linear function which in this senario represents the velocity of the ball.
c is the starting point the height that the ball starts at but since the ball would more likely be on the ground this value
would be 0.
your x value represents time and for any x value you plug in gives you the height of the ball.
so quadratics in real life situations are used to show the distance or movement of an object over a certaint period in time.