Clairvoyance literally means "clear sight", a person with developed clairvoyant abilities has a strong sense of inner vision and is able to receive information in the form of visual images or symbols, most clairvoyants receive their information internally, some say it's a bit like having a TV screen in side their heads with images and symbols being shown, as far as symbols go I use tarot a lot so I tend to see symbols as tarot card images, some clairvoyants receive information externally, physically seeing, mainly spirit people and animals.
Clairvoyance is a term that's is often used incorrectly to describe other psychic abilities than just the visual ability to receive and perceive information, such a clairaudience "clear hearing", clairsentience which is the ability to feel spirit or atmospheres. We talk about being able to see into the future and describe psychics as being "seers" or "visionaries" we all have to some degree clairvoyant abilities, images can come in dreams, daydreaming, although maybe not any so called predictions, you still receive images and that is clairvoyance and can be developed by anyone.
If you are a visual person who easily thinks in pictures and whose language is visually orientated, then it is very likely you will be able to receive psychic/spiritual information visually, for example when asked to describe something you talk about the visual elements, rather than the sounds or smells of the object, then you can easily develop clairvoyance. Clairvoyants may also work in jobs with an artistic element to them, like drawing or painting design etc, you will notice when being given a reading you can normally tell how the psychic/medium is working they will say things like " I see what you mean"," I see you will be" etc, notice the emphasis on "SEE"
There two main ways of seeing, subjective clairvoyance, and objective clairvoyance, subjective clairvoyance is the most common this is internal vision inside the minds eye so to speak, where we conjure up pictures on a screen in side our minds we tend to use this when we meditate, visualization, etc and use the brow chakra this is the point between the eyebrows. Objective clairvoyance is where we see physically, you may see spirit of people, animals, lights, shadows etc, some people I've spoken to with this ability, see spirit as solid and in colour and 3 dimensional, in my experience I see the spirit as like a white solid form, and as far as lights go I see them as like a blue twinkle, but we will all perceive this differently, most commonly you may see something out the corner of your eye, a quick flash of light etc.
I will also mention here "Clairoma" the ability to smell psychically/spiritually you may get smells from loved ones for example there favourite perfume, the smell of baking bread, tobacco, and flowers etc. Clairoma seems to be spontaneous but you can develop this to some extent, by attuning your sense of smell, by smelling flowers and spending time in nature.