What is the difference between a Stock Item and a Non-Stock Item?

What is the difference between a Stock Item and a Non-Stock Item?

1. Stock Items
  1. Stock Items are described as items which can be physically counted when doing stock takes.
  1. Beverage item examples are cans of soft drinks or beer or tots of whiskey.
  1. Food item examples are loaves of bread or cheese and fresh vegetables.

2. Non-Stock Items
  1. Non-Stock Items are described as items which cannot be counted for example Menu items, or anything that is created by using two or more stock items. 
  1. Beverage item examples are Cocktails or wine sold per glass.
  1. Food item examples are Menu items such as Lasagna or Pizza.