The Trim Path feature allows you to draw only a portion of the stroke on a vector shape. This can be used to create a variety of animations where a line needs to follow a path. Every stroke you create for a shape can have its own independent Trim Path.
To activate Trim Path, select a shape that has a stroke and click the stroke options in the inspector. Now, use the Trim Path drop-down menu and select either Sequential or Synced mode. Both modes enable Trim Path, but behave differently when used on a shape with multiple paths.
When Trim Path is set to Sequential, paths are animated sequentially. The order in which they animate is dictated by their order under the shape.
Synced mode animates the trim path along all paths concurrently.
The trim of a stroke happens from a Start point to an End point. By default, all shapes have a Stroke that starts at 0% and ends at 100%. Change these values to modify the position of the Start and End points of the trim (which are represented by a percentage of the full length of the path).
Use Offset to easily move the trimmed portion of the path.