What format is the FIO log?

Could you elaborate on the format of the FIO log? I'm curious to know if it's a text-based file, a database format, or perhaps a proprietary structure. Additionally, I'd like to inquire about its structure and key elements. Does it contain timestamps, transaction details, or other relevant information? Understanding the format will help us better interpret and analyze the data within the log. Please provide a concise yet comprehensive description of the FIO log format.