It's not really something you think about when you're a little kid.
I think I only really started thinking about it in school. I went to a Catholic school with a strict dress code. When we got into middle school, they introduced a church uniform - one day a week, when we had School Mass, we had to wear a different, more "formal" uniform. The girls were required to wear a knee-length skirt and white tights, no exceptions.
Even when it was raining, or freezing cold in the middle of winter, when we'd shiver on the entire walk from our little school building, across the long parking lot to the church, when I was struggling to breathe because my asthma didn't like the cold, we were required to wear these skirts because they were "more presentable for a lady." I was twelve.
It was a little better in high-school, but there were other problems. There were no uniforms, but my friends were constantly caught for having shirts that were "too revealing" - tank tops in the Georgia summer heat - or jeans that were "inappropriate" - the jeans with ripped knees because we didn't buy new ones very often. We were lectured by our teachers about "not distracting the boys" with our clothes and our actions.
When I was 18, I started working as a waitress to pay for my college tuition. The older men that came in called me "baby" and "sweetheart" with sleazy grins while ordering their third beer and looking anywhere but at their wives. I stopped wearing my nametag when I served those tables. "Why don't you give us a smile?" they asked at the end of a nine-hour Saturday-night shift. I was covered in grease and burns and felt like crying. I smiled, and got a two-dollar tip on a $50 check.
I looked for a job to replace this one and found an opening at a local mall for a lingerie store. I was surprised when I started the work. The entire team was supportive. The entire team was quick to praise and gave constructive criticism. The entire team made me feel like I was good at what I did, like I had plenty to learn but could pick it up fast, like I was a valuable team member, a valuable person.
The entire team was made of women, and they'd all seen what I'd seen. They were determined not to let it happen on their watch. I worked hard, loved the work, started loving myself again because I was being shown that I could.
When I started writing, I found many interesting things. I found forums full of authors smugly saying, "it's just science that men are better writers." I found histories of Sappho defining lyric poetry and Shelley defining modern science fiction. I found Twitter users quick to say "do we really need another female's opinion?" I found Malala Yousafzai fighting for education and Amanda Gorman fighting for equality, using their perspective from the inside.
I discovered that other women were frustrated because they found the products they used were overpriced. That they couldn't get a fair deal on cars or car repairs when they went in, but their brothers could get half the rate and a decent explanation. That they were being policed on their tone in the workplace, for being "too aggressive" when stating something they wanted while the men they worked with worded things the same way and were rewarded for being "assertive." That reports about "females in the industry" almost never seem to consult them.
That their guy friends looked at them and said "sexism is blown way out of proportion" while telling them never to walk home alone or in the dark.
That their opinions were less valid when they "pulled the woman card."
It's strange how little you notice these things before they become big enough for the weight to feel almost crushing. Or how much you think about them when you'd rather think of anything else, but you have no choice if you want to be heard.
It's not really something you think about until you realize that you shouldn't have to.