An elder can be the leader of or a leader in the church. An elder isn't always chosen by seniority of age, but one who has studied to show themselves approved in God's ministry and one advanced in spiritual administration. It is a divinely appointed office that is held by men or women who are able to teach sound doctrine, refute error, having believing children, who manage their households well, shows themselves approved and of a good report.
A main function of an elder is laying of hands as written in James 5:16 "Is any one of you sick? He should call the elders of the church to pray over him and anoint him with oil in the name of the Lord". An elder should not be given responsibility if they are unable to fulfill the requirements of the title and they should not be chosen because they are a popular figure in church. Being an elder is a high calling and should not taken lightly. All leadership titles fall under an elder title, for anyone leading must bear the Fruits of the Spirit Gal. 5: 22-23.
"Let the elders that rule (direct the affairs of the Lord's House) well be counted worthy of double honour, especially they who labour in the word and doctrine." 1Tim 5:17