"how do people ''perceive'' you?", such a nice argument!
Without any intention to utilize terminology from psychology I'd briefly say that it means "what do people think of you, what is the lasting impression that somebody has following the initial interaction with you". What will someone think about you, how would somebody "characterize" you following an interaction/communication of, let's say, 10 minutes.
As the fellow italki members suggest, there are many factors which may influence someone's perception of another individual, as clothing, voice quality etc. There are also factors, variables, which influence our own ability to perceive another. No two or more individuals can ever have an identical impression following the introduction to some certain person.
People perceive others according to their own experience, knowledge and ideals. And in order to make this a little clearer I would allow myself a comparison of the human to an animal. A cat which is being introduced to a human will not account the fact that the human is literate since cats are not capable of grammar and literacy. A cat or a dog wouldn't account for the fact that a person has musical education, similarly, because musical skills are very primitively developed in cats in comparison to the musical skills that the average human possesses. Where as, a bird would be intrigued by a human whistling a sweet melody and account for him/her differently than for another who doesn't spell out melodic patterns.
In other terms, people can hardly perceive much higher than their own ability and ideals.