So what is the difference between a “deacon” and an “elder.” 538 - 1 - 7

A very detailed Word Study resource is Dickey, Joshua (2014-01-14). The Complete Koine-English Reference Bible: New Testament, Septuagint and Strong's Concordance. However, I prefer Strong's Concordance for a quick lookup.

With thanks to Strong's Concordance:

Deacon

G1247

διακονέω

diakoneō

dee-ak-on-eh'-o

From G1249; to be an attendant, that is, wait upon (menially or as a host, friend or [figuratively] teacher); technically to act as a Christian deacon: - (ad-) minister (unto), serve, use the office of a deacon.

G1249

διάκονος

diakonos

dee-ak'-on-os

Probably from διάκω diakō (obsolete, to run on errands; compare G1377); an attendant, that is, (generally) a waiter (at table or in other menial duties); specifically a Christian teacher and pastor (technically a deacon or deaconess): - deacon, minister, servant.

We read in Acts chapter 6 that there was complaints that widows were being neglected so deacons were appointed to serve tables. Stephen was one of the first seven deacons in the Christian Church. This freed the disciples to "continually to prayer, and to the ministry of the Word."

As an aside, this was same Stephan who lectured the Sanhedrin concerning hitherto not widely known facts from the Old Testament. He was accused of blasphemy and stoned. As Stefan was dying the heavens opened up and he saw Jesus standing at the right hand side of the father. Jesus standing, not sitting as usual; pretty much giving Stephan a standing ovation.

Elder

G4850

συμπρεσβύτερος

sumpresbuteros

soom-pres-boo'-ter-os

From G4862 and G4245; a co-presbyter: - presbyter, also an elder.

An elder may be “A senior forefathers a term of rank or office among the Jews members of the great council or Sanhedrin (because in early times the rulers of the people, judges, etc., were selected from elderly men) of those who in separate cities managed public affairs and administered justice among the Christians, those who presided over the assemblies (or churches)”

G4862 - A primary preposition denoting union; with or together (but much closer than G3326 or G3844), that is, by association, companionship, process, resemblance, possession, instrumentality, addition, etc.: - beside, with. In compounds it has similar applications, including completeness.

G4245 - Comparative of πρέσβυς presbus (elderly); older; as noun, a senior; specifically an Israelite Sanhedrist (also figuratively, member of the celestial council) or Christian “presbyter”: - elder (-est), old

My take away from all this legalistic language is that deacons are the workers and the elders are more elevated both in stature and in authority. That said, at His first coming Jesus was the suffering servant. Like Jesus, Stephan was not too proud to be a servant and wait table even as he performed miracles.