Richard Feynman was one of the great scientists of the 20th century, making significant contributions to physics and other related fields. Part of what made him stand out was his gift for teaching. He had a remarkable knack for explaining some of the most complex things in ways anyone could understand. He was also a model of the desire to deeply understand how things worked, often deriving a result in several ways to be more confident he was right.
The Feynman learning technique is typical of how he approached understanding something deeply and helps explain some of his teaching skills.
Now, you can explain it because you deeply understand it, too.
"You can know the name of that bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird."
— Feynman's father, from Surely You're Joking Mr Feynman?