What Is It?

The priority field sits in the SNP2 tab of the product location master and controls quite a bit of cross module functions in SCM.

In PP/DS

It controls the order by which material is scheduled in PP/DS. Thus for all production orders for a specific date and for a specific production line (priority can only be used to sort among products to be applied to similar resources) the priority helps to sequence the production orders.

In SNP

Used for the deployment optimizer and in capacity leveling. However, since the deployment optimizer is rarely used, it is primarily in effect for capacity leveling.

Conclusion

Overall the priority field is a very simple field that can affect both PP/DS and SNP. I have run into it as used by PP/DS for sequencing.