Yuri Gagarin was the first person in space, but Alexei Leonov was the first without a wimpy spaceship in the way. Alexei Leonov and Pavel Belyayev rode the Voskhod 2 ( "voshkod" means "ascent" or "dawn") to the most hostile environment humanity can reach. Then Leonov proved that humanity can take it.
Leonov pictured above the entire world, AS IS ONLY RIGHT AND PROPER FOR SUCH A MAN.
Leonov spent 12 minutes in utterly open space. The only scientific function of this spacewalk was to see if he'd survive it. Never mind the human body -- back then the world's rocket scientists didn't even know what space would do to spacesuits, which is why the high-pressure oxygen supply inflated Leonov's suit so much that he couldn't get back into the capsule. Unless Leonov wanted to stay in space for the rest of his life -- which would be less than an hour -- he'd have to do something amazing.
Luckily, doing amazing things was his entire job, career, and legacy. Ditto Ed White, seen here, who did the same thing 11 weeks later.