Zapier is a workflow automation software that allows users to create custom notifications for calendar events, automate recurring tasks, and send reminders to themselves or others. With Zapier, users can set up automated workflows, known as Zaps, that perform specific actions based on triggers, such as sending a text message before a meeting starts. Users can also create their own Zaps to customize notifications and add filters to further tailor their automation. By using Zapier, users can save time, stay organized, and increase productivity by automating routine tasks and reminders.