That's called "Friends with Benefits"
Basically, it means, u have sex, but stay friends with no relationship
A friend can be a lover and a lover can be 'just' friends! Sexual intercourse is involved with a lover, mental and emotional intercourse are more the realm of a friend. Hence, the categories need not be mutually exclusive!
You stay in touch with them, but continue to make more friends.
Sometimes you can continue to be friend, but sometimes you can't. It depends if you are sick of her or if you really care about her
Its hard and definatly something that you and your friend will have to work out. If you and that person were friends before than you can continue to be friends but you have to keep it Professional.
It is quite normal for a friend to talk about other friends and thus, if you have other friends feel free to talk about them. If your friend is simply talking about friends and then waiting for a reaction from you then ignore it. Continue on with your other friends and don't worry too much about this friend and what they want to discuss.
Move on and continue as friends knowing that a relationship could ruin the friendship.
You could try and get them to talk things out to be friends again and if not you will have to divide your time between them to continue to be friends with both. Try not to get involved in their dispute directly.
Its when friends have know each other for a long time, and their friendship will continue for the rest of their days.
Your mom and your friend's mom obviously are not getting along, but that should not have anything to do with being friends. Continue seeing you friends and let your mothers resolve their own problems.
If I am Jack's friend, and I am your friend, that makes me a mutual friend. That's all it is. A friend you have in common with someone else. Mutual friends are a good way of deciding whether to accept a friend request. If you have several mutual friends, but don't recognise the name, it can help narrow down where the person knows you from. :)
Let them know. If they are a real friend, they will understand and will want to continue to be friends. But if they intended to make it a "serious" relationship, they will probably not talk to you anymore.
Just continue being friends. He's [I am presuming your friend is male; that may not be correct] doing the work; you have no obligations.