I've learned 朋友 as a unit as a word for friend. When I look up the two characters I see that they both mean ... friend.
It seems 友 is often used as a last part of words meaning something with friend, like 好友 for good friend.
What is the difference of 朋 and 友? Do they have slighly different meanings when used separately, or are they identical in meaning and just used in different situations?