When particles form solid substances there may be a creation of a lattice which determined the properties of the solid formed. Lattices are not created only between covalent molecules. They can be made up of ionic molecules, ions or even atoms. The term lattice only refers to a regular arrangement of particles. They are usually created due to inter-particulate forces of attraction.
The arrangement of particles in a lattice leads to a crystalline structure and identifies the properties of the substance like solubility, melting and boiling points, interaction with light, etc. These properties can be used to identify many types of substances.