The Gospels are a set of stories about the life and teachings of Jesus, written by people who lived in the time of Jesus, but long after his death. These stories were not written down until the time of the first century A.D., most of them around 70 A.D. That means that there were at least 40 years between the time Jesus lived and when the writers wrote the stories down.
The Gospels are considered to be reliable because they were written by people who either witnessed Jesus' life or talked to people who did. The writers accurately described the political and cultural context of their day. Plus, a variety of historians and scholars from that time have used the Gospels as reliable sources for their research. In addition, archaeological evidence has been found to prove that some of the events in the Gospels happened.
Overall, the Gospels are believed to be reliable information about Jesus' life and teachings. They provide an important window into how Jesus lived and the beliefs that the early Christians had about him.