Have you ever seen one of those failed karate skill videos online, the ones where the karate “master” is attempting to break a stack of bricks or boards to show how impressive he is, yet all that happens is a very sore hand and an even bigger bruised ego? Well, the Eat Your Comics intern never had, so when he got the idea to smash boards with his fist because he's “so much stronger than even Captain America, it's no joke,” it was no surprise to everyone else that he failed miserably. This was even despite the boards being made of balsa wood, the kind of wood that's so weak you can break it by looking it wrong.
Oh! You mean the white guy doing Kung Fu and showing off his awesome chest tattoo? Yeah. I can tell you about Iron Fist.
In the same way that Luke Cage's Power Man was created to cash in on popularity of the blaxploitation movies of the early 1970s, Iron Fist was a way to draw in fans of the martial arts craze of the same era. Iron Fist, or Danny Rand as he's known when he's not wearing his mask, was created by Gil Kane—who also created the modern Green Lantern—and Roy Thomas—who followed Stan Lee as Marvel's Editor-in-Chief.
Danny Rand's parents died on a quest to seek the mystical city of K'un L'un, a quest they somehow thought was wise to take a boy of 9 on. Yet, Danny was the only one of the party to make it to the city, where he trained under Lei Kung. Ten years later, he manages to kill the Shou-Lao the Undying, a dragon of immense power guarding his own heart, which had been ripped from his chest. Danny defeats the dragon, which ends with him plunging his fist into the dragon's heart, and he is forever marked by a dragon tattoo on his chest. Now that he's super powered, Danny leaves K'un L'un and, as the Iron Fist, searches for Harold Meachum, the man who failed to save Danny's father when he had the chance. However, because he's a good guy, Iron Fist does not kill Meachum but lets him live. Yet, when Meachum is killed by a ninja, Iron Fist is blamed. He is only able to clear his name with the help of detective duo, Misty Knight and Colleen Wing.
Later, Misty and Danny fall in love, which is why he helps fend off a brainwashed Luke Cage trying to kill her. Once they get that all sorted out, and the villain behind the plan is taken care of, Danny and Luke team up to create Heroes for Hire, which is exactly what it sounds like, superheroes acting as private investigators and bodyguards for hire.
Like every modern superhero, Iron Fist has died and come back to life. In his case, he was switched with a doppelganger grown from plant matter and who had his full memories. The switch was made by the ancestral enemies of K'un L'un, the H'lythri, plant-like beings from another dimension. They kidnapped Iron Fist for some diabolical purpose, but he was soon freed by Colleen Wing, Misty Knight, and Namor the Sub-Mariner. Since then, he's briefly taken on the role of Daredevil while Matt Murdock was in jail to help—unsuccessfully—convince the world Murdock isn't Daredevil; he's trained a new hero going by the name of Power Man, a kid named Victor Alvarez; he's joined the New Avengers and stood up agains Norman Osborn's Thunderbolt-esque Avengers; he's trained Hope Summers in how to use the Phoenix Force; and he's reformed Heroes for Hire with Luke Cage.
Iron Fist is both the name Danny Rand takes on when he's being super heroic as well as the name of the source of his power, which, again, he earned by punching a dragon's heart. Sometimes comic books are just amazing. Being the Iron Fist, he is able to focus his chi to enhance his natural abilities. One of the most notable ways he can do this is by focusing his chi into his fist, making it glow and grow incredibly hard and strong, like iron. (Now does his name make sense?) It takes a lot of focus, so he can't use this ability in rapid succession; originally he could not use it often at all, but he's grown stronger throughout the years and doesn't take as long to recoup. Another way Iron Fist focuses his chi is inward to heal himself or outward to heal others.
Bonus Trivia: The reason Luke Cage and Danny Rand are best friends in the comics? Their solo titles weren't doing so well after the short-lived reign of their respective sub-genres, so Marvel decided they should join up as Power Man and Iron Fist. In reality, rather than both leaving their own titles and joining forces, Iron Fist joined Power Man's book starting in issue #48 and remained part of the duo until the end of the series with issue #125.