Animation
CSS animation changes property values over time using keyframes and animation properties.
Animations can repeat, alternate, delay and use timing functions. For interface work, motion should be purposeful and should respect reduced-motion preferences.
Motion defined by keyframes
Animations can repeat, alternate, delay and use timing functions. For interface work, motion should be purposeful and should respect reduced-motion preferences. In practical terms, Animation belongs to the presentation and layout layer. Knowing that layer is important because it tells you what the term can change, what it cannot change, and where to look when something behaves unexpectedly.
Moving through named states over time
@keyframes pulse can animate opacity or transform over time without JavaScript.
Where looping motion belongs
You do not need to memorize the term in isolation. It becomes useful when you can recognize it in the tool, browser, file or conversation where the concept is doing real work.
Animation and transition are not interchangeable
CSS animation changes property values over time using keyframes and animation properties. By contrast, A CSS transition interpolates between an element’s old and new property values when a change occurs. The two can appear in the same project, but they describe different parts of the work and should not be used as interchangeable labels.
The mistake: animating without purpose or restraint
The common mistake is to use Animation as if it also meant Transition. That blurs two separate decisions and usually sends troubleshooting in the wrong direction. A better test is practical: Prefer transform and opacity for smoother motion, and honor prefers-reduced-motion.
Why motion needs a state model
In day-to-day work, Animation matters when the concept needs to be identified precisely instead of being grouped with a nearby term. The practical value is not the vocabulary itself; it is being able to identify the right control, file, setting or decision when the concept becomes relevant.
@keyframes pulse can animate opacity or transform over time without JavaScript. That example is useful because it turns the definition into something you can recognize, test and discuss with other people working on the same project.
Related terms worth learning next
Sources and further reading
Use these references when you need documentation-level detail, specifications or product-specific behavior beyond the plain-English explanation above.