Short answers, pulled from the story.
The Group of 77 was founded on the 15th of June 1964, when 77 non-aligned nations signed the Joint Declaration of the Seventy-Seven Countries at the United Nations Conference on Trade and Development. The group has retained its original name despite expanding well beyond its founding membership.
As of 2023, the Group of 77 has 134 member countries, plus the UN observer State of Palestine. This is nearly double the 77 founding members, though the group keeps its original name.
The G77 holds that developed countries bear historical responsibility for greenhouse gas emissions and points to the large disparity in per capita emissions between rich and poor nations. As a result, the group often resists binding emissions reduction commitments on its members, arguing that economic development and poverty eradication must take priority.
China appears on the G77 membership list but does not consider itself a member. Since 1994, China has made financial contributions and provided political support to the group. Official statements are issued under the name The Group of 77 and China to reflect this unusual arrangement.
The Charter of Algiers was adopted at the G77's first major meeting in Algiers in 1967. It established the basis for the group's permanent institutional structures and was developed under the leadership of Raul Prebisch, who had previously worked at the Economic Commission for Latin America.
The Group of 24, or G-24, is a chapter of the G77 established in 1971 to coordinate developing-country positions on international monetary and development finance issues. Every G-24 member is also a G77 member. Its chapter is based in Washington, D.C., near the International Monetary Fund and the World Bank.