An eephus pitch is a pitch thrown with a four seam or any grip, frankly, on the baseball.
The eephus pitch ranges anywhere from 10 to 20 feet in flight. It is a pitch that throws off the batter's eye level, and one in which the pitcher releases it ideally with normal arm and body speed. Dave LaRoche, New York Yankees pitcher in the 1970s, was famous for throwing an eephus pitch. It was known as the Lob, named after LaRoche, in which he threw the ball 15 to 20 feet in the air as it landed softly into the catcher's glove, deceiving many hitters.
The eephus is a very difficult pitch to master, and I don't recommend young pitchers to play around with it. Although certainly, it's a fun pitch for players to toy around with in practice.
This is how you throw an eephus pitch.