Glamouring

Glamouring is a magical ability to change one's appearance to look like another human being. Whitelighters and Elders naturally posses this ability, while other witches must use spell or potion to activate the change. Some Warlocks also possess this ability as well, although it was used more by Paige throughout the course of the series.

In 2000, Darklighter known as Spirit Killer was also seen to possess this ability, which he used to change his clothes into uniforms to prevent the possibility of getting suspicious or exposed, rather than completely changing his appearance.

When used by a Whitelighter, the changes looks like the being is Orbing and then returns to his/her natural identity. With a Witch and Whitelighter-Witch, they get surrounded by white orbs, it also works this way for normal witches. Unlike the others, Warlocks morph into the human they're trying to be.

Unlike Shapeshifting, the glamour creates an illusion around one's body, whereas shapeshifting makes an physical change on them.

In the Book of Shadows, there is a specific spell To Change One's Appearance. The spell was used in Morality Bites Back, to change the appearance of Elise Rothman back into the way she looked when she was attacked by Cal Greene.

Anton
Anton was a powerful 1920's Warlock who seduced Phoebe's past life, P. Russell to the side of evil. In order to trick her cousins, P. Baxter and P. Bowen, which happened to be the past lives of Piper Halliwell and Prue Halliwell, her sisters, Anton glamoured into Priscilla's former lover, so P. Russell would be able to attack P. Bowen without P. Baxter stopping them. He came back out of it when he attacked P. Baxter.

Paige Matthews
Paige first used this power in the Season 5 episode, House Call. After getting put under a hex, she changed her appearance into Glen Belland's fiance's, Jessica, so Paige would be able to marry Glen not Jessica. She hid Jessica in Purgatory, while she orbed back to earth. Leo eventually found out what she had done and returned Jessica back. She also used this power through Season 7 and Season 8.

Leo Wyatt
Leo first appearance of this power was in the Season 3 episode, Power Outage. In order to train the sisters for their fight against Belthazor, Leo glamoured into him and attacked the girls. Phoebe was able to kick him using Levitation, while Prue used Astral Projection to appear behind and kick him away so Piper would be able to cut a bit of his flesh off him. After the training, Leo glamoured back into his normal self. He also used this power in the Season 6 finale, It's A Bad, Bad, Bad, Bad World, Part 2, to trick Gideon.

The Charmed Ones and Leo Wyatt
In Season 7's, Something Wicca This Way Goes...?, The Charmed Ones and Leo glamour themselves into entirely new identities. The sisters, tired of demon fighting, decide to permanently glamour themselves, (as well as Leo) in order to fool everyone after their defeat over Zankou. These new outer-images are temporary. In the beginning of Season 8, we see the sisters and Leo with new identities.

Phoebe Halliwell
Unlike her youngest sister, Paige, Phoebe most likely used a potion and/or spell to active the power to glamour. The first time she used this power was in the Season 6 episode Hyde School Reunion, however it is unclear whether she was using a spell or empathically channelling Paige. She later used the power in the Season 7 episode, Something Wicca This Way Goes...? to glamour herself into a new identity. She also used it multiple times in the Season 8 episode, Still Charmed and Kicking. The last time she's seen using this, is when she reveals herself to her ex-husband, Dex Lawson. She glamours herself back into Julie Bennett, an alias she picked. She then glamours back into herself. She also glamoured into Victor to help send a message to the Underworld.

Piper Halliwell
Just like Phoebe, Piper probably used a spell and/or potion to glamour and used it multiple times in the Season 7 finale and the Season 8 premiere. One of the most known occasions where Piper has used it was in the Season 8 episode, Mr. & Mrs. Witch. Piper glamours into a mortal who has been working with a demon to kill another mortal man. After the spell is reversed, Piper glamours into the man and tells reporters that he killed the man, after the reporters leave, Piper glamours back to normal. She also glamoured into Wyatt to send a message to the Underworld in Season 8 premiere, "Still Charmed and Kicking".