What is an it girl slang?

Understanding the Term 'It Girl'

An 'it girl' refers to a young woman who is not only visually appealing but also possesses an engaging personality, making her particularly charming. The term was popularized in British high society in the early 20th century. An iconic example of an 'it girl' from that era is Clara Bow, featured in the 1927 film poster for 'It.'