Each layer property has a time-vary stopwatch icon (
) that you click to begin the animation process. Once the stopwatch is active for a specific property, After Effects automatically sets new keyframes whenever you change the current time and the property value. When the stopwatch is inactive, no keyframes are present. If you type a value for a layer property while the stopwatch is inactive, the value remains in effect for the duration of the layer.
A. Selected stopwatch B. Deselected stopwatch