The term “Gyaru” is a Japanese slang for “Gal” (girl), but it’s a Japanese cultural expression, which is used as a term for a fashion sense, used by the Japanese girls sometimes or sometimes women who grow up as “Gyaru”.
“Gyaru” is a unique fashion style, where the girls dye their hairs in bright colours like blond, pink, green, etc. and use creams to make their skin look browner, while wearing trending clothes and highly decorated nails to make themselves stand out from the crowd.
The term and style “Gyaru” originate from the 1970s as a street fashion, but it became popular in the 1990s and early 2000s, thanks to the American action drama TV series called Baywatch.
The whole style wasn’t as flashy as nowadays as they would only use blonde and lighter colours to dye their hair and highly decorate their nails, to stand out.
“Gyaru” is a Japanese cultural thing, which became well known outside of Japan, thanks to the Japanese culture spreading to the western audiences, like anime, manga, movies, and games, where usually there is a “Gyaru” character in place.
The style is not as popular nowadays, since the whole scene has died down as people like more minimalistic things.