How keyframes and time work

Every property animation in a project is the same small thing: a property, a starting value, an ending value, a moment to begin, and a duration. There are three ways to create one — the Animate a value panel at the top of the inspector's Anim tab, the ◆ diamonds next to each field, and ● record mode — and they all produce exactly the same kind of animation. What makes all three make sense is one idea: a starting value can be left open, meaning "start from wherever this property already is." Understanding that, and how animations on the same property chain together, is the whole mental model. The Graph Editor (see Fine-tune motion in the Graph Editor) draws that shape as a curve — its two draggable ends are the start and end values described below, plotted rather than typed.