Hi,
Physical material helps you define how object colliding with this surface will behave. You may want to define a floor as sticky, or sticky ( think ice vs grass).
You likely want to set that up front during editing. In the case of trigger info, it's used to find out ( if you want ) about the material properties to know how to react based on the friction value of the colliding object. that's already some very advanced use of trigger info.
bye,
Jean