When you add a keyframe, Blender creates an "action" in the background. You can edit it in the Action Editor (as a property inside the Dope Sheet Editor - first editor in the bottom editors shown in the video). The Dope Sheet Editor(second editor in the video) lets you tweak multiple actions; disable "Only Show Selected" to view all keyframes. The Timeline (replacing the Dope Sheet Editor in the video) is a simpler way to manage keyframes, sometimes needed for things like scene keyframes. To view all keyframes, go to View > disable View Only Selected. The NLA Editor (third editor to the right in the video) lets you turn actions into strips for advanced control: playback speed, looping, blending, and more.

Note: for simplicity, Action Slots and Graph Editor are ignored in this Blendtime Story