Each person is equipped with a set of sensors which gather information, these are sight, hearing, touch, smell and taste. These sensors can be stimulated in a number of ways, and the mental process used to describe this stimulus is called 'perception,' and putting this one stimulus together with others, to make a meaningful whole is called 'interpretation' and this is how people make sense of the world.
Although all people should have the same capacity to use their senses to gatehr information, capacitites do differ from one person to the next. Genetic differences, aging, accidents and other things all can lead to impairment of senses. More importantly, people have learnt to perceive things differently because of encultration.
People's perceptions are influenced by their expectations.