Drawings from Draw are there.
A tag names a run of frames (an animation): it plays on its own, exports as its own GIF, and game engines read it from the spritesheet's .json.
Making it smaller cuts off what falls outside, on every frame (undo brings it back).
Parallax: how fast the layer moves in the ⇆ parallax preview. 0 = stays put (a sky), 100% = moves with the ground, more = passes in front.
They start as Aseprite's. Click one and press the new key (Esc: cancel, Backspace: no key). Always there: Space + drag to move around, Alt+click to pick a colour, Shift while drawing for straight lines, Shift / Alt when selecting to add / take away, Esc and Enter for a selection, the arrow keys to nudge it.
A named area for game engines: a hitbox, a UI box that stretches (9-slice), or a point things hang from (pivot). Exported in the .json and .aseprite.