What does it mean to be a witch to you?

I am not a witch, but lot of my friends are. Recently I moved from Czechia to UK to study there. I met lot of new people and after some time I discovered that about half of them are practicing witches. I never met a witch before, so you must understand how curious it made me. I asked them what does it mean to them that they are witches, but I found out that for them it is very personal and not something they openly share. I don't want to intrude on anyone privacy, but still want to better understand culture of my friends. My question thus is what does it to you mean to be a witch? I know that it is a very individul, but I hope that asking more people will help me understand it.