Shoe lining is an important part of the construction of a shoe. It consists of two components: an insole and a pac. An insole is a removable or built-in insert that is placed inside the shoe to provide cushioning and support for the foot. A pac is a thin, flexible material that is used to line the interior of the shoe and provide additional comfort and protection. Both the insole and pac are essential components of a shoe's lining and help to ensure a comfortable fit.