The Kinsey Scale, also known as the Heterosexual-Homosexual Rating Scale, is one of the oldest and most widely used scales to describe sexual orientation.
Though outdated, the Kinsey Scale was groundbreaking at the time. It was among the first models to suggest that sexuality isn’t a binary where people could either be described as heterosexual or homosexual.
Instead, the Kinsey Scale acknowledges that many people aren’t exclusively heterosexual or exclusively homosexual — that sexual attraction can fall somewhere in the middle.
Source: 10 Kinsey Scale FAQs: What It Is, How to Use It, Accuracy, and More