The safety stock is the stock you hold extra on top of what you expect to sell. It would be best if you had this buffer to react to unexpected events in the future. You can think of a peak in your sales or a new delivery that is delivered too late. This buffer depends on the product category, the variability in the sales history and the supplier's security of supply.
For example, a product in the A category from a reliable supplier sold five times daily will have a low safety stock. A highly variable product with an unreliable supplier will have a higher safety stock.
