iCal is a calendar application that allows users to manage multiple calendars, subscribe to other calendars, and sync schedules across devices. It helps users be more efficient by notifying them of upcoming events and meetings. Teachers can use iCal to notify students of events and create to-do lists. The document discusses how iCal can help students manage their time and work with other Mac applications like Address Book. Users are tasked with adding practical features to iCal like adding a birthday calendar, event, alarm, and attendees.