Today, the autumnal equinox is the first day of fall. It's also one of the two days a year when the north and south halves of the world face the sun in equal amounts. During the fall, the days start to get shorter. That's because our planet is actually titled in space. When it's fall, that means your area is pointed further away from the sun causing longer nights and shorter days.
When fall approaches, the green-colored food making chlorophyll of plants is no longer needed, which is what leaves us the beautiful other colors. Evergreen trees like pines, cedars, spruces, and firs stay green all winter because their leaves are covered with a thick wax and their insides hold materials that help them not to freeze.
Bottom line, it's the most beautiful season of the year if you are lucky enough to experience it.