It's a single tale for young kids, written in 1932 by Soviet writer Arkady Gaidar who took an active part in Russian Civil war (he became commander of a regiment at the age of 16!).
The tale romantisize a revolution and struggle against capitalists (aka "буржуины" (bourgeoisie)). The full title is "Сказка про военную тайну, Мальчиша-Кибальчиша и его твердое слово" (A tale about Military Secret, Malchish-Kibalchish and his Word).
It tells about young kid who fought the enemy army and knew an important Military Secret (yes, from capital letters
), bad guys (non-Soviets) wanted to know it and captured him. But M-K was brave and true to his word, he died, but didn't tell the Secret.
Um, that's all (I ommited a few details about the family, a bad kid, who betrayed him and great glory, which awated the boy after his death
).
So basically Мальчиш-Кибальчиш cam mean anything; that he's brave, romantic, reckless, younf, stubborn, xenophobic or just liked this book when he was a kid (it's really had a romantic vibe about it, a communist version of "15 y/o captain", only M-K was 7-10 y/o, I think).
Here is tale in Russian with a lot of pictures (I had the the same book when I was five).
http://www.army.lv/maljchish/main.htm