The adjective 'elder' refers to people only. It is one of those words which you really don't need to learn or use. As a comparative adjective, 'elder' is an alternative to 'older' in one case only: when it comes before 'brother' or 'sister'. For example, you can say 'I have two older brothers' or 'I have two elder brothers'; you can say 'Anna is my older sister' or 'Anna is my elder sister': the meaning is the same. However, you can't say 'Anna is elder than I am': you have to say 'Anna is older than I am'. You also have to use 'older' to talk about everything, and everyone, other than your siblings. Is the adjective 'elder' useful in modern English? No, it isn't. You can forget about it - just use 'older' in all cases, and you won't go wrong.

Im no grammarian but generally elder is a noun and older is an adjective. That man is an elder in my church. He is an man of some distinction. (It doesnt have anything to do with his age.) I have an older sister. Or: I have a sister who is older than I. My sister has more years (was born before)

Older = used to compare to people. But when referring to two people members of the same family use "elder" not "older". Also, "elder" is a word that means "senior, experienced or exalted person, and a leader of a tribe/society/town/town-hall or any similar societal structure."