Gender is one of the most complex human experiences. While many people identify with the gender assigned to them at birth, this is not true for everyone. Those who do not want to mold themselves into a male or female are beyond the binary. They are called non-binary.
Some people who are nonbinary experience their gender as both male and female, and others experience their gender as neither male nor female. These people have both masculinity and femininity in their colorful personalities. While non-binary is often seen as a new idea, the descriptor has been around for as long as civilization has. In fact, nonbinary gender was recorded as far back as 400 BC. As far back as 200 AD, the Hijras, people defined in India as beyond male or female, are referenced in ancient Hindu texts. India is one of the many countries in the world with a language and social culture that accepts those whose gender cannot be categorized as male or female. When someone comes out as non-binary, it can be a little bit confusing about the pronouns to use. The bottom line is that it's best to go with whatever the individual's preference is. Many non-binary people use "they", while others use it in conjunction with other pronouns. Like she/they for example. Asking whether to refer to someone as they/them or any other pronoun may seem strange at first, but it is one of the simplest and most important ways to show respect for someone's identity.