Didimauw, pipesmokingtom has it down pretty well. Fountain pens feel great to write with, the result is a classier look on paper, etc. They feel a lot nicer in the hand than most ballpoints.
I have three Lamy Safari pens, one each with bold, medium, and extra fine nibs. Not a tremendous investment. Love them all, use them all. They are great for sketching out designs for my customers, adding a special touch to a signature or written correspondence, and taking a minute to reflect while you reload with ink. I have misplaced my pens at home, but never lost one in my four years of ownership which is a marvelous.
Used to mix my own purple ink for them, that was a lot of fun!