COP stands for 'Conference of the Parties' and these are United Nations conferences on its different conventions. COP15 is where world leaders come together to talk about biodiversity and how to tackle it, as it's the COP for the United Nations Convention on Biological Diversity.
These discussions cover all forms of life from microscopic viruses to enormous whales, as well as conservation, knowledge-sharing and financial policies associated with these organisms, their protection, and their use.
The first meeting took place in 1994 in the Bahamas, and COP15 is the latest to take place. Due to the COVID-19 pandemic, it has been split into two parts, with the part taking place virtually in 2021, and the second part taking place this year in Montreal, Canada.