Memorial Plaque Sayings What Is The Difference Between A Church Plaque And Church Memorial Stone?

What is the difference between a church plaque and church memorial stone? - memorial plaque sayings

In trying to do my homework on RS. Does anyone know the difference between a plaque and a memorial stone in terms of importance in a church? (I know that a) made of wood or brass and the other is the stone and also what this meant in the window? and what is being represented?
thankyou