Ownership is a mechanic added by SecurityCraft. It is used to secure the placement and settings of Reinforced blocks. Once a Reinforced block is placed down, only the player who placed the block down (the Owner) can destroy the block afterward. This helps to prevent griefing from other players and reduce damage done by mobs and explosives. To non-Owners, the block is unbreakable and explosion-proof. The only way for non-Owners to destroy Reinforced blocks is by breaking them in Creative mode. Having Ownership of a block also prevents non-Owners from inserting Modules into it or changing any of its settings. Ownership of a Reinforced block can be transferred to another user by using the Universal Owner Changer.
Owners of Reinforced blocks will be displayed in WAILA's tooltip if the player has that particular mod installed.