Although highly characterized as hearing voices and seeing shadows, there are several types of hallucinations. Keep in mind that the examples on this page are just the common examples, in theory, anyone can hallucinate practically anything. Throughout this page, you'll even find examples of hallucinations that occur in completely healthy people! The following are different categories of hallucinatory experiences.
These include hearing things that aren't there. One may hear hums and rhythmic sounds and random noises, such as the sounds of different animals, phone alarms or notifications, knocking on doors, songs or melodies (either known by the person or not), sounds from nature like the wind blowing or rain falling, etc. Auditory hallucinations can be 'unformed', meaning they sound distorted in some way, or 'formed', meaning they are fully clear.
This is a subcategory of auditory, useful to distinguish because of how common these are! 'verbal auditory' is just a really fancy science jargon way of saying hearing voices. Voices can be positive but are commonly negative. There is substantial research showing that the nature of someone's hallucinatory voices is affected by the surrounding culture of the society they live in, with western individualistic societies producing more negative voices. They can be someone known to the person or not, whether that's a real person or a fictional character. They can be mumbling/whispers/indistinct conversations as well, voices may also argue with each other or comment on things that you are doing. Human vocalizations which are not speech, like crying, laughing, screaming, breathing, singing, etc. also fall under this category.
These include seeing things that aren't there. Nearly all visual hallucinations can be classified into distortions of size, shape, and/or colour. The popular stereotype for this one is shadow people and monsters, but you can also see weird shapes and colours in your vision. Visual snow syndrome is a constant visual hallucination of a static overlay over your vision. Sometimes people see things like bugs or random objects; personally, I've seen walls and ceilings move before. A visual hallucination that everybody experiences are heat waves! When you see that little distortion in the distance when it's hot, that's obviously not actually happening, but it's still an effect created by the way our eyes work. These are often called 'mirages'. Many people also will see 'aftereffects' when they look at the same thing for a long time and then suddenly look away to a different scene - you'll see shadowy afterimages, which resemble hallucinations, but again are just completely healthy functioning of the human eye.
These include feeling things that aren't there. Common ones are bugs crawling on one's skin, or hands touching you that aren't there. Sometimes, there are feelings of organs shifting or something turning around in their stomach or skull, or feeling something inside your body trying to get out of it. A tactile hallucination that healthy people may occasionally experience is feeling their phone buzz as if they got a notification. I personally experience it to a heightened amount due to my psychosis, but when I asked people without psychosis if they experienced it, they immediately recognized what I was talking about and said they experience it occasionally.
These include smelling things that aren't there. It's not impossible for this to be a pleasant smell like flowers or perfume or freshly baked sweets, but they're very commonly unpleasant and weird, like garbage, smoke, burning rubber, rotting food, burnt toast, chemicals, a metallic odor, or a moldy or stale smell. Sometimes people can't identify the smell. Sometimes the smells linger, or they go in and out.
These include tasting things that aren't actually there, commonly rot or poison or a strong metallic taste. Another example is a strong sweet taste like molten sugar. Sometimes they're described in terms of taste (bitter, sour, sweet, disgusting) but can be more specific like chloroform, charcoal, tobacco, rusty iron, blood, sperm, bile, garlic, grilled, peanuts, oysters, or mussels.
These include feeling your body or the room moving when it isn't. People with Parkinson's have reported feeling sensations like flying or floating. They can also include feeling the room move when it isn't, or out of body sensations. One that I experience is that the world moves around like an elevator or treadmill. They can also include imagined sensations, like a feeling of bliss. These hallucinations can be called tactile hallucinations as well most of the time.
*I'm not sure on the name because they're never referred to as synonyms directly, but from what I've seen they refer to the same kinds of hallucinatinons.
These include feeling that someone is in the room with you, is nearby, or is standing behind you. These can be hard to distinguish from delusions of persecution or reference, but are distinctly sensory phenomena instead of a delusional thought process that can occur separately. They are noted to be a common type of hallucination in Parkinson's.
These are hallucinations which occur when you're waking up (hypnapompic) or falling asleep (hypnagogic.) They're considered normal and aren't a cause for concern, but may be more common in people with certain sleep disorders (for hypnapompic hallucinations.) Hypnagogic hallucinations are mainly visual, but obviously there are a large variety -- when I get them, they're often tactile or auditory!
Illusions are like a "lesser" form of hallucination. Whereas hallucinations involve perceiving something that's not there, illusions are misperceiving something that is there. For example, it's common for humans to see faces where there are none due to pattern-seeking. Illusions may also be things mistaking running water for a voice, and there are also various bodily illusions like feeling like you are lacking an arm or that you are not in control of your body.