The snow ball is a projectile.
The snow ball is dropped by the snow golem.
The snow ball can be used to craft the snow block.
Snow balls can be fired from dispensers.
When the player shift clicks while holding a snow ball, it will be fired. Snow balls are affected by gravity. While they cause damage to mobs, fired snow balls do not interact in any way with the player.
These will presumably be fixed in 1.29 when snow balls become part of the new projectile code.
- 1.28: When fired by a snow golem, the snow ball moves at a slower velocity.
- 1.28: While they cause damage to mobs, they fly straight through the player.