There are certain tasks and varieties that are always paid the same. Pay Templates allow you to specify rules for common Job configurations. For instance, if you have a specific task or variety that must be paid a minimum-wage during picking, you can create a template for that.
Each field above is optional and defaults to "Any". The last three fields (Default, Min, Max Piece Price) are the rules that get applied to piecework jobs. So, if you were to set a $5 default piece price to "Picking" task with no other filters, any "Picking" piecework job would get defaulted to $5/pc for whatever piece types are selected.
This is intended to be broad by default, but able to be as specific as you'd like. You could configure something as general as "Always pay any piecework greater than $1" or as specific as "Picking Honeycrisp in Buckets style at Ranch A (Block B) at $20/bucket".