If you are doing filet crochet, the spaces are open spaces where there is a chain ( or two) between the double crochets forming a mesh fabric. The x’s indicate double crochets in the mesh spaces to form a more solid design.
There should be more info in the pattern telling you how many chains between the DC’s, and how may DC’s to put in each x’d space.
It does tell me how many chains, etc. Thank you for responding. Have a great day!