You can see and edit frames that make up the animation on the timeline.
The basis of the entire animation is keyframes or keys. They contain the poses set by the animator.
These are the main poses of the "jump in place" animation. For each pose, there is a key on the timeline. The keys are dark blue.
In the end, the character should assume the same pose as in the beginning. Therefore, this key can simply be copied.
The first and last frames of the animation are displayed under the timeline. When there are a lot of frames it is convenient to limit the visible area of the timeline to work with.
You can move and copy entire groups of frames. Let's make another jump like that!
By creating new keys and changing the poses in them, you create an animation. The button for creating and deleting keys is located on the toolbar above the timeline.