Depending on the type of edger you purchase, it may be able to do the job of a trencher or trimmer, both of which perform similar tasks to those of an edger.A trencher is essentially an edger than can dig deeper and wider, usually with greater efficiency. Often, a large-bladed edger will be referred to as a trencher.An edger that uses a string (common on electric options) to operate can function as a trimmer, too. While edgers create vertical boundaries, trimmers create horizontal edges. String trimmers are also known as weed eaters or weed wackers.