Parallax is the apparent shift in position of an object when viewed from different angles. For example, when you look at a tree close to you and then glance at a mountain in the distance, the tree seems to move against the background of the mountain. This effect helps us understand depth and distance in our surroundings. In astronomy, parallax is used to measure the distance of nearby stars. By observing a star from two different points in Earth's orbit around the Sun, astronomers can calculate how much the star appears to shift against more distant stars. This method provides valuable information about the universe.