Do you know how you ask your parents or friends for their opinion before making a big decision like what game to buy? Scientists also ask many publishers (papers, articles) to collect their opinions on a single topic called a systematic review.
So, a systematic review is when scientists decide to answer important questions by gathering and analyzing information from all the publishers available. They have a particular way of finding the best publishers and rules for how they will combine all the information from the selected publishers. Then, they can decide what the results mean and share this information with others. It's like looking for a lot of puzzle pieces to put together to get a complete picture.