These two terms answer different questions. Smart Animate answers "what changes?" It looks at two frames, finds layers with matching names, and animates their position, size, rotation, opacity and other properties from one frame to the other.
Easing answers "how does it change over time?" Figma lets you pick a standard curve such as ease-out, a custom cubic-bezier curve, or a spring. Spring easing is defined by physical settings, stiffness, damping and mass, rather than a fixed duration, so motion speeds up and settles the way real objects do.
The real difference appears in code. In a product, a spring can start from the current position and speed of an element. If a user interrupts a transition or flicks a sheet, the motion continues naturally instead of jumping. A prototype transition plays the same way every time, which is fine for showing intent but does not show how the motion behaves under real input.
So a Figma prototype is a good reference, but developers still rebuild the motion in code. To keep values consistent, many teams save spring settings as motion tokens. Our free Figma Animation to Spring Converter turns Figma easing into spring settings you can use in code.
If you want the interactive version to be the deliverable rather than a reference, a tool with a runtime is needed. ExodeUI, which we make, stores states, springs and events in one file that runs in the app.