Keyframes animate a clip's properties over time: set a value at two moments and the editor interpolates between them with the easing you choose.
Open the keyframe editor Select a clip and open Animation → Keyframes. The editor shows a track per property: position, scale, opacity, rotation, volume.
Set the first key Move the playhead to the start moment, then set the property's value. A key is recorded at that time.
Set the second key Move later in the clip and change the value again. The preview now animates between the two keys as you scrub.
Shape the motion Pick easing per segment: linear, ease-in, ease-out or smooth. Position keys can be dragged directly on the canvas.
Stack properties Combine tracks freely: a fly-in usually keys position + opacity together; add scale for a pop.
Tips
Volume keyframes double as manual audio automation, so you can fade a music bed under one specific line.
Keyframing works on overlays too: PiP fly-ins are two position keys and two opacity keys.
The export compiles the same curves the preview plays, so timing never drifts.