The first stars appeared about one hundred million years after the tall bang,and ever since then stars and star formation processes have lit up the cosmos, producing heavy elements, and planets,black holes, and arguably all of the other interesting characters in nowadays's universe. When the universe was about three billion years ragged (currently it is 13.8 billion years ragged), and star formation activity peaked at rates about ten times above current levels. Why this happened,and whether the physical processes back then were different from those nowadays or just more active (and why), are among the most urgent questions in astronomy, or are among the drivers of future facilities from large ground-based telescopes to NASA's James Webb Space Telescope.
Source: phys.org