Appointments are the fancy stuff that have no acoustic or structural effect on the guitar. They exist solely as decorative elements. Some people find fancy appointments showy or pretentious, but a great guitar is a work of art to behold with the eye as well as the ear. So go for the bling.
Typical appointments include intricate neck inlays (such as abalone figures countersunk into the fretboard), a fancy headstock design, and, on an acoustic guitar, the rosette, or decorative design around the sound hole.
One subtle aspect about appointments: You may think that the only difference between two guitars is in the appointments — for example, a fancy inlay job may seem to be the only thing that distinguishes between a certain company's Grand Deluxe and Deluxe models. But the truth is that the more expensive guitar — although nominally the same in materials and construction — often gets the choicest materials and enjoys higher quality-control standards.
This situation is just a Darwinian reality. If 12 pieces of wood, all destined to become guitar tops, come into the factory, slated for six Grand Deluxes and six Deluxes (fictitious titles, by the way, bearing no resemblance to actual guitar models, living or deceased), the six best pieces of wood go to the Grand Deluxes and the six next-best pieces to the Deluxe models. They may all share identical grading, but humans with subjective powers decide which models get which tops.