A charmed creature has been persuaded that the one charming it is not an enemy. More precisely, in the eyes of to the charmed creature, the personal reputation of the creator of the charmed effect is increased by 50. This generally means a cessation of hostilities towards the charmer, but this can be quickly nullified by further actions (e.g. the charmed creature will still protect its friends if they are attacked).
Many sources of being charmed impact appraise checks, but simply being charmed does not.