This day commemorates the day in 1948 the United Nations General Assembly adopted the Universal Declaration of Human Rights.

The date December 10th was chosen to honor the United Nations General Assembly's adoption and proclamation, on 10 December 1948, of the Universal Declaration of Human Rights (UDHR), the first global enunciation of human rights and one of the first major achievements of the new United Nations. The formal establishment of Human Rights Day occurred at the 317th Plenary Meeting of the General Assembly on 4 December 1950, when the General Assembly declared resolution 423(V) inviting all member states and any other interested organizations to celebrate the day as they saw fit

The day is normally marked both by high-level political conferences and meetings and by cultural events and exhibitions dealing with human rights issues. Besides, it is traditionally on 10 December that the five-yearly United Nations Prize in the Field of Human Rights and Nobel Peace Prize are awarded. Many governmental and non-governmental organizations active in the human rights field also schedule special events to commemorate the day, as do many civil and social-cause organizations

The Universal Declaration of Human Rights (UDHR) is a milestone document in the history of human rights. Drafted by representatives with different legal and cultural backgrounds from all regions of the world, it set out, for the first time, fundamental human rights to be universally protected

What are the Declared Human Rights we all have?
https://www.ohchr.org/en/human-rights/universal-declaration/translations/english