By default, all clips display a level envelope curve. The envelope consists of three parts: the fade in part, the sustain part, and the fade out part.
The points on the left and right side of the curve are the fade in and fade out junction points that separate the fade parts from the sustain part. The gray points at the start of a fade-in and at the end of a fade-out allow you to see small fades even when you have fully zoomed out.
The envelope curve indicates if points, fade ins, or fade outs have been defined. In addition to the curve, changes in the level envelope are also reflected in the waveform.