What's the difference between an "Ally" and a "Friend"?

To extend on this point:

• Allies generally have common interests (e.g. similar foundational principles or common enemies) which leads to cooperation in an effort to make said interests come about and/or maintain them.

• A friend is literally a friend. Somewhat of an extension of an Ally. Not only would they have common interests, but the cooperation that said interests lead to in turn leads to friendship.

E.g. Allies: Demacia and Piltover both have an issue with the Noxus-Zaun alliance. Demacia and Piltover also have conflicting ideals, but the threat of an Enemy outweighs it and they cooperate out of immediate necessity.

Or to put it more simply,

I would go into battle with an ally But I would only go to bars with a friend.

Aatrox x Tahm OTP