Trim Path allows for the animation of the start, end, and offset of a path, allowing for a shape, stroke, or both to be drawn on the screen.
Trim Path is found under the Shape category within the Effects Browser.
1, Trim Start: [ Default 0 ] [ Range 0 - 100 ]
Sets the trim start position on a stroke
2. Trim End: [ Default 100 ] [ Range 0 - 100 ]
Sets the trim end position on a stroke
3. Trim Offset: [ Default 0% ] [ Range 0% - 100% ]
Offsets the trim start and end position as a whole
Allowing for the animation of strokes.