Gender is not just a column in an application form to check like a multiple-choice question, it is way more than that. There's history, mythology, and most importantly biology involved in it. But typically people stuck up with the concept of the gender binary and believe genders other than male and female, are abnormal, unacceptable, unethical, and impractical. Apart from knowing about the penis and vagina, there are a few more important things a person needs to know.
Generally, gender identities revolve around a person's genitals and that's how medically and biologically, any infant can get recognized as a male or a female and not any other gender identity, especially during birth because one can't feel the identification crisis or sexual emotions or intimate feelings of a newborn child. Hence, people conclude a kid's gender identity by looking at one's genitals. A penis with testicles makes that kid a male, and a vagina makes that kid a female. Well, this is the most common and basic procedure of recognizing a person's gender identity.
There is a huge exception with identifying the gender of a kid during birth, and this can be seen in the cases of Intersex children. Intersexuality is a gender identity rather than a typical sexual orientation. This has to do everything with the hormonal imbalance, chromosome shuffling, and blended external genitalia. This is proper biology and it is more than acceptable as everything happens inside the womb of a mother. Due to various medical conditions during pregnancy, a few mothers may give birth to kids who have blended gender identities.
You can find an intersex child with internal masculinity and external feminine genitalia and similarly internal femininity and external masculine genitalia. Some kids contain XX chromosomes which produce male hormones but externally they are blessed with a uterus and at the same time some kids have XY chromosomes that produce female hormones but they are externally blessed with a penis. Here you may decide instantly as male or female but gradually within no time, a person can be identified as an intersex person.
But there is one more case where you can rightly recognize a kid as an intersex gender during birth. It is being true gonadal intersex. Here a kid may have XX, XY, or both chromosomes in the same body and may be blessed with a penis or a uterus or blended genitalia. Yes, in these kids you may find a penis without testicles but with ovaries and a vagina with hidden testicles and without ovaries. It is complex to understand unless you know the typical anatomy of an intersex person. But this isn't weird, invalid, and unnatural. This is an extremely common yet rare phenomenon in gender identities.
And next come, the feelings, after a kid reaches one's puberty phase and gets to know, explore and understand things around in every possible way, mostly sexually, the gender identities become visible and easily felt. Male kids develop facial hair, base vocal cords whereas female kids develop breasts and changes in internal biology like menstruation. But if you consider external changes as gender identities then you may go truly wrong.
A person can be identified as transgender when that person feels that his soul is stuck up in the wrong body and yearns to get into the right body in which the soul matches it. An externally masculine-looking kid may feel feminine inside due to unmatched or excess or low hormones in the body. This is quite common and it directly affects a person's behavior, personality, attitude, emotions, and feelings. This is how, a kid realizes that he or she isn't a typical male or female, but a transgender who needs to be transitioned to the other or opposite gender to make things right physically and mentally.
Male, Female, Transgender, and Intersex are the gender identities that depend on the typical masculine and feminine traits and genitalia which also means, these revolve around the gender binary. But do you know that there are 70 extra gender identities and many other deeper classifications which has nothing to do with the gender binary?
After growing and getting matured, a person may realize many things when it comes to gender with one's sexual explorations, romantic attractions, social and societal involvement with the surroundings in and around one's self. There is no mandate rule that a person must stick to these typical gender binary identities. There are gender identities way more beyond than just a male and a female. And all these gender identities come under the umbrella term of Non-binary.
So, if you don't feel like a complete male or complete female or both male and female, or partially male but not female, partially female but not male, and if you also may feel that this masculinity and femininity doesn't befit your personality and you don't want people to identify you as one gender identity or both gender identities, then yes, you are valid, your identity is valid, your feelings are valid, your opinions are valid, your emotions are valid, your tastes are valid, your preferences are valid, your likes and dislikes are valid, your whole concept of gender is valid. Do you know that there is a gender identity that is completely based on your ego and only you can know about that and no one else can?
Well, you don't have to conclude yourself as a typical male or female or third gender (according to the world politics), you can remain as gender non-binary person and if you still don't like to be confined to any term, it is still fine. Things have changed because now you don't have to tick forcefully in male and female boxes, you don't have to push yourself in the option of others, there is a flexibility of not mentioning if you don't like to mention but the world is running towards gender diversity, hence you find various boxes in which you feel you can befit perfectly.
You don't need to know every single gender identity on earth, but you must know that your gender identity is not the only one that is valid and force others to accept your stupidity. Genders are fluid and flexible, not rigid and restricted. Period.