As per image below...
In a store banner and its sidebar the terms 'Departments' and 'Categories' are used interchangeably. I feel it would be better to use a consistent terminology throughout. From a buyer point of view that would probably be 'Departments' as it is called a 'Store'.
Country name : United Kingdom
Country code : GB
Agent : Mozilla/5.0 (Linux; Android 7.0; SAMSUNG SM-T580 Build/NRD90M) AppleWebKit/537.36 (KHTML, like Gecko) SamsungBrowser/6.2 Chrome/56.0.2924.87 Safari/537.36
Viewport : 980w x 1386h