Premonition

Premonition is the ability to see and experience events from the past, present, and future. This power is said to be highly desirable, since it often helps a witch evade dangerous situations.

Phoebe Halliwell developed this power while she was in her mother's womb. It had been bound during her childhood and adolescent years but was activated again in 1998. She triggers the power by touching objects or people related to the Premonition by way of Psychometry.

Psychometry
Usually in the early stages of Premonition, most users receive their visions by touching objects or people related to the Premonition by way of Psychometry. As their power grows, users get visions out of the blue, and are able to look into the future, present, or past by will alone.

On rare occasions a user may choose to touch an objects or a person to get a vision by will: Kyra, a demonic seer, has been known to do this. If the psychic energy in an area is strong enough, a psychic will get a vision without touching anything, even if their power hasn't evolved yet.

Visions
Usually, in the early stages, most users can only see what is taking place. As their power grows, users develop the ability to experience aspects of their premonitions allowing them to hear what is taking place within the environment of their visions and to feel the emotions of the victims in their premonitions. Phoebe can sometimes feel the emotions of the victims in her premonitions, for example, she once felt the the emotions of an elderly woman being killed.

Calling for Premonitions
Users can train themselves to call for premonitions. Phoebe learned to do this less than a year after gaining this power. She was able to call a vision to her using Piper's plane ticket, allowing her to see Piper missing her plane. Before, this didn't always work, as evidenced on multiple occasions. However, her power grew stronger when Prue's "spirit" arrived back on Earth, Phoebe can now look into the future, present or past at will. Also, demonic seers can call premonitions on will, everytime, and they can always see what future will be if the present situation continues.

Precognition
Users can see and perceive the future in a Premonition. This is the first branch of the power Phoebe Halliwell developed when her powers were reawakened.

Retrocognition
Users can see the past in a Premonition. Phoebe's original Precognitive abilities grew to include retrocognition, to see the past. The first time she used it was when she touched a locket that Prue Halliwell gave her and saw 300 years into the past. Later as her power grew she was able to see multiple events in one vision. An example of this was when Phoebe touched the Book of Shadows and saw seven different events in one vision.

Clairvoyance
Users can see the present in a Premonition. This ability is used to discern locations and gain information about objects, beings, or places. Phoebe gains this extension of her original Precognitive abilities early on in the series.

One notable instance of Clairvoyance was when Phoebe psychically connected with the Succubus and was able to see through her eyes to locate her next victim. Later she was able to speak through the Succubus and helped Prue resist her deadly lure.

Another memorable instance was when Phoebe and Piper were attending their friend Brittany's funeral. Phoebe wanted to know how Brittany died, so she impulsively touches the coffin and receives a vision of the present, seeing Brittany looking very old.

Kyra was demonic seer who was very adept at using this ability. She used it to track down Inspector Sheridan in the mental hospital, and hours later, used it to uncover Leo's secret: he was an Avatar. It's reasonable to assume that she also used it to protect herself by evading attacks.

Astral Premonition
Astral Premonition is the ability to project one's consciousness into a future or past event, either as a physical astral form, through the body of one's future-self, or through the body/ memory of a past being, such as Mata Hari. This allows the user to experience a premonition first-hand. This is a combination of Premonition and Astral Projection and is the closest a Charmed One has gotten to natural Time Travel. The only known user of this power is Phoebe Halliwell. It allows her to see things in more detail and to stay within the future for a longer period of time.

Enhanced Intuition
As a by-product of Premonition, a user can sense and predict situations before they happen. It's most useful to sense and predict attacks. Kyra was a powerful demonic seer who was also very adept at sensing attacks.

Phoebe Halliwell also has great intuition due to her Premonition power. She is also sensitive to magical shifts in time. When the demon Tempus repeatedly reverse the day, Phoebe senses straight away that the day feels familiar and gradually remembers more and more. She says in her own words that because her power allows her to see different things in different times, she must be more susceptible to the time shift.

Sharing Visions and Psychic Echos
Two psychics can share visions with each other by holding hands, palm to palm. They can also create Psychic Link with each other, either purposefully or accidentally. The latter was demonstrated by Bo Lightfeather, who accidentally created a psychic bond with Phoebe. With him stuck in a time loop, Phoebe received the same injuries he sustained at the time.

Phoebe can share her premonitions, and received premonitions, with other psychics. She also once developed a psychic link with a Succubus, though it's unclear how she connected. The Seer was able to send Phoebe a premonition from the Underworld. Phoebe was also able to share the vision shared with her by Kyra, with an Elder.