Trails just don’t spontaneously appear. They are planned, built and blazed so people can travel safely from trailhead to summit and beyond. The purpose of a trail marker (or blaze) is to help hikers follow a given path. It is used to indicate things such as the beginning and end of a trail, a change of direction or an intersection.
Blazes are found on prominent trees that are easy to spot on the trail. They are usually placed just above eye level – or slightly higher in areas that receive snow. Painted markers are roughly two inches wide and six inches tall, while other types of markers and signs may vary in size.
Learn more here: https://www.greenbelly.co/pages/how-to-read-hiking-trail-signs-markers-blazes