Move the timeline marker to the in or out point of a layer
Move the timeline marker to the next visible keyframe
Trim the work area to the position of the timeline marker
Move the in or out point of a layer
Trim the selected layers to the position of the timeline marker
You can change which layer you have selected in the stacking order by combining the Cmd/Ctrl key with the up and down arrows
Move the timeline marker one frame forwards or backwards
Resize and re position a layer to match the width of the composition, whilst preserving the aspect ratio