People are usually confused with the terms of biological gender (or biological sex) and gender as they tend to use them reciprocally. However, albeit intimately tied, these two terms are different and are describing distinct concepts.
In principle, gender is determined by the society and by extension by the socially constructed norms.
Biological Sex can be defined as the biological differences between men and women and the dissimilar physical characteristics that determine humans as male and female.
To the contrary, according to FAO, (social) gender is not determined biologically, but is constructed and transformed by the societal environments in which humans interact. It is culturally shaped and defines established behaviours of the different sexes, both perceptual and material, and affects the overall actions and behaviours between men and women.
As such, sex is not equivalent to gender per se, and gender does not refer to biological sex necessarily.
As such, the biological gender (sex) entails natural characteristics of humans which are easily definable, and (social) gender is a broader concept which entails a range of dynamic characteristics, which are the following:
meaning that humans from their early childhood learn how to behave based on societal stereotypes, which are changing over the years.