Question

what is the difference between grana and stroma?

Answer 1

stroma is the matrix of chloroplast .
thylakoids are disk shaped structures present in the stroma. A number of thylakoids form a column like structure called grana.
I hope this will help u

Answer 2

Grana are stacks of membrane bounded, flattened discoid sacs(called thylakoids) containing the molecules of chlorophyll.
Stroma is the homogeneous matrix in which grana are embedded.