The moon can appear larger when it is near the horizon because of an optical illusion known as the "Moon Illusion." This illusion is caused by the fact that our brains perceive objects in the sky as being at a specific distance, and when the moon is near the horizon, it appears to be closer to us than when it is higher in the sky.
Additionally, when the moon is near the horizon, it is often viewed in comparison to trees, buildings, and other objects on the ground, which can make it appear larger by contrast. This is similar to the way that an object appears larger when it is viewed against a distant background, rather than when it is viewed against a closer background.
It is important to note that the moon does not actually change size in the sky, and the Moon Illusion is simply an optical illusion that is caused by the way our brains perceive the moon's distance and size.