crontab is a Unix-based utility that allows users to schedule tasks to run automatically at specified intervals. It uses a simple text file format to define commands and their execution times, making it easy to automate repetitive tasks like backups or system updates. Each entry in a crontab file consists of time and date fields followed by the command to be executed. Users can set tasks to run every minute, hour, day, or even on specific days of the week. This flexibility makes crontab a powerful tool for system administrators and developers alike.