Edge Completion refers to how a span is offset from the sketch line. The default is to offset the span from the sketch line without trimming or extending it. Leave the Start, End, or both checkboxes unselected for this option.
The Trim/Extend option will trim or extend the span to intersect the angle bisector for the sketch point with which it is associated. In the trim/extend example below, end A has been trimmed and end B has been extended.
The Connect at Distance option first trims or extends the line, then connects it to the sketch point. Enter a value in the Connection Distance field to adjust the length of the span before connecting. In the example below, the connection distance of 5 shortened the span by 5 map units on each end. The Connection Distance field does not support negative values.