The Moon moves right to left, passing through the penumbra and umbra. Credit: NASA's Scientific Visualization Studio RFK Jr. Says He’s Rehiring Thousands Of People He Mistakenly Fired Kurt ...

Earth produces two shadows, the penumbra & umbra. Think of the penumbra as the lighter outer edge & the umbra as the darker inner core. As the Moon enters the penumbra (edge), it will begin to darken.