Zapier is a workflow automation platform that integrates with thousands of apps from partners like Google, Salesforce, and Microsoft. The platform allows users to create automated systems for their business-critical workflows across their organization's technology stack using interfaces, data tables, and logic. To set up this workflow, the user needs to create a Zap by clicking on the Create Zap button, then setting up a trigger, which in this case is Microsoft To Do. The user authenticates the app with Zapier, selects the desired list from the app, and sets up the parameters of their action in Notion. Once set up, the workflow will automatically upload tasks created in Microsoft To Do to the selected Notion database.