Next to your Commander Bonuses you can assign your Skill Points strategically to give different bonuses for Units and Buildings and increase their benefits. You get Skill points each time you level up your Commander.
The Skill points configuration can be reset using a special item from the Store
Above the Skill Tree you can check out your remaining Skill points.
In most of the cases, the lock on the Skill means that it is not unlocked and you have to assign more points to previous skills.
However, in the case of the Trap skills the lock means that the feature is not yet available but you can assign points for skill further down the Skill tree.
❗You can not assign Skill points to Trap skills because the feature is not implemented in the current game play.