Counsellor and councillor are very commonly mixed up – you find them everywhere, from non-fiction books to blog posts and all points in between. I suppose both of them try to help people – but they are different words for different things, and they need to be kept separate and understood as such.
A councillor is someone who sits on a council. So, local councillors are those people we elect to sit on the city council and run bits of our lives for us. Oh yes, let’s not forget our capitalisation rules in all the excitement: Councillor Broomfield sits on Libroville City Council. She is a councillor who sits on a city council.
A counsellor is someone who provides help with personal problems. They give counsel, they counsel you. Maybe that’s the way to remember it, as you can’t council someone. Can you? You go for counselling with a counsellor (I have seen the two spellings being mixed up even in that context) and maybe that’s the way to remember it.
If anyone has any nifty ways to remember these differentiations, do post a comment!