silk isnt needed for any board design(doesnt affect electrical connect etc). its more of an aid for future troubleshooting, and population(is the designation text on the board, such as U23, or R2). Typically silkscreen is also used to document your company name and the board name. if you are creating a component , it is good practice to create a silkscreen to show the boundaries of the component, the component designation, and typically a polarity marking. This is usually automatically generated in PADS if you are using one of its built in component creation tools.