Extroverted Feeling, or Fe, used primarily by ESFJ and ENFJ as a dominant function, and by ISFJ and INFJ as a secondary, is a natural understanding of and ability to play off the emotions of others.
It is similar to Te in that it is outwardly goal- and schedule-oriented, but it bases its strategy for completing these goals upon personal empathy/careful observance of local social and cultural standards (as opposed to Te's focus on impersonal/theoretical constructs) and is keenly aware of the emotional states/probable emotional strengths and weaknesses of others based on how they interact socially.
Fe makes friends very easily and, if used for malicious purposes, can and will use the emotions of others to manipulate them into participating in its plans. For healthy Fe users, though, it's usually just a strong sense of open, heavily emotional support for friends and loved ones--ExFJs are great people to go to when you want to feel better about yourself.
Fe differs from Fi because it changes with cultural surroundings. It gets its sense of morality from the social standards of its community (sense of community/fitting in is VERY important!), and so if an Fe user moves from one culture to another he may significantly change his standards in these areas in order to integrate into the new community/gain trust and emotional influence with others. (Fi, used by xxFP types, will rarely change its moral standards at all because they come from the inside.)
So people with good Fe are typically VERY charismatic because they know how to phrase everything in just the right way to appeal to the emotional/cultural sentiments and values of their audiences. You won't catch an FJ using coarse language or anything that could potentially be construed as offensive in important, public image-related situations very often at all--this is the kind of mistake they almost never make, and one that many NTs would do well to learn from.
And be careful of crossing the Fe doms, especially (ESFJ/ENFJ)--because some of them who don't have the restraint to behave otherwise will use the emotions of others to manipulate them into disliking you. Watch out.