Direction, Logo, Previous Page
This is a triangle with a sharp corner pointing to the left, which is usually used as the "Back" button. This symbol is somewhat similar to the play button, except that the triangle points differently.
It should be noted that the background colors will be different on different platforms. For example, most platforms display blue frames with different shades, Google platform depicts orange background colors, Facebook platform displays gray background frames, and some platforms do not display background frames. As for the color of triangle, most platforms use white, and some platforms choose black, gray or blue.
This emoticon is commonly used to indicate the action of turning to the previous page when reading books.
