
Volleyball was designed for (but not restricted to) the indoors.
Initially, there was also no restriction on the number of players. However, the first game was played with 5 players on each side.
The objective of the game was (as it still is) simply to keep the ball in the air over the net.
Around 1920, the rules evolved to limit teams to 6 players and 3 contacts with the ball a side.