> This is a factual description. Is your gender on the same side as your biological sex? That's all cisgender means today.
That may seem reasonable, and I certainly wouldn't want to argue against it, but I've seen enough discussions around these questions to know that what's written there is not entirely uncontroversial.
Firstly, even an indisputable fact can be offensive if you mention it in a context in which other people consider it to be entirely irrelevant.
Secondly, some activists vehemently deny the existence of "biological sex". They insist on talking about "gender assigned at birth" instead. I can tell you from experience that arguing with those people is not always productive.
Thirdly, although standard English uses two different pronouns for people, "he" and "she", so gender is an undeniable social fact in any community that speaks standard English, some languages (probably most languages) don't have gender so "gender" isn't such a simple factual thing in those communities. You may be able to infer gender from roles in society, behaviour or clothing styles but it's less clear.