You can expand the Timeline panel to make it easier to work with numerous objects, or you can make the Timeline panel smaller to give yourself more room for the slide stage. The Timeline shows where animation occurs in a document, including frame-by-frame animation, tweened animation, and motion paths.Controls in the layers section of the Timeline let you hide, show, lock, or unlock layers, as well as display layer contents as outlines. You can drag Timeline frames to a new location on the same layer or to a different layer.
To change the number of layers and frames that are visible, resize the Timeline. To view additional layers when the Timeline contains more layers than can be displayed, use the scroll bars on the right side of the Timeline.
The content is represented by gray frames, or gray frames with a dot in them. Motion-tweened content is represented by a blue tween span, which is part of frames that you can chose seperately or also use it as a single selection. Flash displays shape tweens as a series of light-green frames, with an arrow drawn between keyframes. Shape tweens and motion tweens are created and manipulated in different ways, which you will learn in the sections that follow.
Tween spans and static content are selected in different ways. Static content and shape tweens are selected as a single frame if you are in the default frame-based selection mode. New motion tweens use a span-based style of selection (even if you have frame-based selection active), which will be familiar to you if you’ve tried the span-based selection model in previous versions of Flash.(http://www.adobe.com/devnet/flash/learning_guide/animation/part03.html)
The art of animation is all images changing over the course of time in a natural, pleasing, and entertaining manner. It’s the same whether you’re creating a cartoon with a long-eared rabbit or you’re developing a presentation for the next quarterly sales meeting. Elements move, change shape, and change color. In Animate, that means that the properties that define an element change over the course of time. Those properties and their changes are tracked on the timeline through the use of keyframes—those little diamond-shaped markers.(https://www.safaribooksonline.com/library/view/adobe-edge-animate/9781449342913/ch04.html)