The Timeline records each feature you use to create a parametric design in Fusion.
Since it captures parametric design history, the Timeline is only available in Parametric Modeling mode.
You can edit, rename, suppress, and drag features forward or backward in time, organize features into groups, and create selection sets. You can use the buttons to the left to roll the design history to the beginning or the end, play back the design history, or step through the individual features.