The simplify function allows you to remove non-essential points from the selected feature(s). The simplified feature(s) will look similar to the original(s) but with fewer points.Note that comments and other attributes attached to the removed points will also be removed.
The smooth function allows you to round the sharp corners of the selected feature(s). The smoothed feature(s) will look similar to the original(s) but with more points. The smoothed feature(s) will retain the attributes of the original(s).
Tolerance
This value represents the largest deviation that the simplified or smoothed feature will have from the original.