This is the 14716th most frequent Polish word.
półce
"Półce" means "shelf" (dative or locative case) in English.
Here, 'półce' is the locative case of 'półka', indicating the location where the book is situated.
Książka leży na półce.
The book is lying on the shelf.
'Półce' again represents the locative case of 'półka', specifying the shelf on which decorations are located.
Na tej półce są różne ozdoby.
On this shelf, there are various decorations.
'Półce' locatively states the area of the search and here indicates the shelf involved in the activity.