The Unicode standard supports skin tone modifiers and other modifiers for gender and hair colours.
Your phone keyboard likely allows you to specify your preferred skin tone, gender, and hair colour either generally or on a per emoji basis, or sometimes it just lists all variants.
In many areas, particularly posts, we convert the default native emoji character into an image. We also provide some alt/title text which is why phrases for those.
As for our emoji picker and autocomplete we haven’t yet provided a way to pick anything other than the default variant. This was partly due to time constraints when we first developed the feature and partly due to not really having an ideal way to present a UI to select skin tone and other...