What is Pundit or CanCanCan in Rails?

Pundit and CanCanCan are popular authorization gems. Pundit uses plain Ruby policy classes (PostPolicy) with methods like update? and destroy? that return true/false. In the controller: authorize @post checks if the current user can perform the action. CanCanCan centralizes authorization in a single Ability class: can :update, Post, user_id: user.id. Check with can?(:update, @post) or authorize! :update, @post. Pundit is preferred for complex, object-level authorization; CanCanCan for simpler role-based access.