Safety stock is a measurement of reserve stock to protect empty stock and reorder point is a level of inventory to take action for stock.
There are a few types of MRP planning (MRP types) under the more general concept of consumption based planning. The more automated one is when the system calculates by itself the reorder point and the safety stock (VM).
For the system to be able to doing this, you must define and run material forecast before. System is using the results of it for these calculations.
Basicaly, ROP is calculated as the forecast basic value * by the lead time, to which safety stock is added. Safety stock is calculated based on the forecast variance.