Server logs are records of events that happen while a service is running. They are like a notebook showing when a request arrived and how the service responded.
If a website returns an error, a developer may check its logs to find clues about what happened around that time. Logs can help explain problems that are hard to reproduce on someone's computer.
Logs should not contain passwords or other sensitive details. They are useful records, but they need limits and careful handling to protect people's information.