001 LINEAR Easing
The following four images are hopefully self-explanatory. But in case they're not... image one has no smoothing applied. Image two has smoothing set to 100% on the first key. Image three has smoothing applied on the first and last key at 100% and image four just has smoothing applied to the last key at 100%.
The following sets of four observe this pattern.
This is the same as 'Smooth'