Big Bang Nucleosynthesis refers to the process that occurred within the first few minutes after the Big Bang, where the universe was hot and dense. During this time, protons and neutrons combined to form the first atomic nuclei, primarily hydrogen, helium, and small amounts of lithium and beryllium. This process set the stage for the formation of stars and galaxies. The conditions of the early universe allowed for nuclear reactions to take place, leading to the creation of these light elements. The abundance of these elements can be observed today, providing strong evidence for the Big Bang theory and helping scientists understand the universe's evolution.