However, one can recreate a specific player's head with the command /give skull 1 3. There is no way to obtain the player head in survival mode without cheats. The dragon head is obtained by entering the Outer End and breaking the head on an End ship which can be found next to some End cities. The Wither skeleton head may be obtained by killing wither skeletons, and as of 1.8, the creeper, skeleton, and zombie heads may be obtained by killing the respective mob with a charged creeper explosion. Player head (only via creative mode or commands).They are only used for decorative headwear.
Heads are decorative blocks, added in 1.4.2 - The Pretty Scary Update, that can be placed in the world, or worn by any humanoid mob or player as a helmet though they offer no protection.