El Capitan has long been considered one of the premier rock climbs in the world. Today Tommy Caldwell and Kevin Jorgeson completed the first free climb of the Dawn Wall. Overall it took them 19 days of perseverance and determination. Congratulations to both of them for a safe and outstanding climb.
Why is this significant? Climbers have been up El Capitan since the late 1950s, but not always via the same route, and not always via the same method. The most common way to ascend a face like this is through aid climbing. In aid climbing you are allowed to use devices to pull yourself up and stand up via rope attached to fixed or placed protection. The device might include a mechanical ascender, or prusik hitch.
Tommy and Kevin were able to do the route via free climbing. Free climbing is where a climber ascends the wall via standard rock climbing techniques (placing protection and ascending via hands and feet).