Hi Strube, there are various different circumstances it's possible for edges to end up getting cut up into small segments. Sometimes that can be annoying because it then leaves evidence of that segmentation in some construction techniques.

The merge command will merge together 2 smaller segmented edges into a longer single edge. In order to be merged the edges must be smooth to one another and only have 2 edges meeting at a common endpoint.

I've attached an example file, try doing a fillet on the top edge of the cylinder in the attached file, then do a merge on it and compare that.

To do the merge you can either select just the edges you want to merge, or you can select the whole object and it will try to merge all edges it can find.

- Michael