The diference between covalent molecule lattice and covalent network lattice
Covalent molecular compounds are actual molecules. Examples include $\ce{H_2O, NH_3, CO_2, N_2, I_2, SO_3, N_2O_4}$ etc. They are made of molecules which are made of covalently bonded atoms. Covalent network compounds form a network of bonds, and the whole object can almost be considered a "molecule," such as diamond (C network), silicon (Si network), graphene (C network), and black phosphorous (P network).

It's not a coincidence that all but one of the covalent molecules that I listed are gasses at room tenperature and pressure. The intermolcular bonds between molecules are relatively weak. On the other hand, every molecule in a network solid is surrounded in a network of strong covalent bonds.