Gender
Nature, Sex
noun
The kanji and the word are exactly the same. That means they share meanings as well.
性 is a somewhat formal word to talk about gender and sex, including sexual desire or activity. It's also a common suffix to describe the nature of something. 安全性 refers to how safe something is by nature, for example, and ウィルス性 describes something virus-caused, like viral pneumonia.
This has the same reading as the kanji you learned, meaning you know the reading!
性のところ、女性に丸しておいたよ！
In the gender section, I circled female!
この本は、性教育のための本です。
This book is for sex education.
体の性差は、性ホルモンの働きによって作り上げられているのです。
The physical differences between sexes are created by the action of sex hormones.