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The "Bend" of a soccer ball is explained by the physical principles of the Magnus Effect and Deflection.
Similar to Bernoulli's Principle on airfoils, the Magnus Effect happens when the air a ball is traveling through follows a longer path around one side of the ball than the other. This is due to the spin attributed to the ball from being struck by a player's foot. The air following the longer path is moving faster than the air on the other side causing a drop in air pressure on that side of the ball. The ball will then be pushed toward the low-pressure side, causing Deflection.
Just like an airplane leaves behind a wake of turbulence in flight, so does a soccer ball. The spin of a soccer ball causes the air to deflect to one side (depending on spin). The air in turn, pushes back on the ball, which puts the forces of the Magnus Effect and Deflection in the same direction, giving us the "bend" of a soccer ball.