The diagrams often differentiate in some ways. Here are a couple of ways. * Sometimes the diagrams will contain an X within it's "lattice". These represent the frets and strings at which to place your fingers. * Occasionally you may see x's within the lattice that represent finger placement. * They may be vertical-style (fretboard perpendicular to floor) or horizontal-style (fretboard parallel to floor). Many people prefer horizontal-style because it is similar to tablature. Here is a good text-based explanation of how a chord diagram works.