ABC inventory divides the stock in three different category. In a simple manner we can consider 

A as fast moving item

B as medium moving items

C as slow moving items

Now one can easily understand that the consumption of A items means fast moving items will be highest in the market. so the stock level will be less compared to other. It results 70%-80% of annual consumption value and approx 20% of inventory items. The B items has medium consumption value. So it covers 30% of total inventory value and 25% of consumption rate. In last C items are known as slow moving item and has a very low demand. It covers a large space in inventory and has lower than 5% of annual consumption rate.