First entry is the first approach of the tool towards the part. User can specify from where the tool should come to approach (enter) the part and whether there will be a macro move when entering the part or not.
Default setting is clearance area. So the tool comes from the clearance are, moves to the rapid distance and before entering the surface to the feed distance. Setting first entry from rapid distance or feed distance you have a closer start point.
Choose between:
From Clearance area
Use Rapid Distance
Use Feed Distance