How does wind form?
Wind is air in motion. Wind forms when the sun heats one part of the atmosphere differently than another part. This causes expansion of warmer air, making less pressure where it is warm than where it is cooler. Air always moves from high pressure to lower pressure, and this movement of air is wind.
During the day at a coast, the sun heats the air above the land more quickly than the air above water. The warm air over the land expands and rises. Cooler air from the ocean moves toward the land to take the place of the rising air, and makes a "sea breeze" that cools beachgoers in the summer. The image below illustrates the circulation of air.