The Inbox is your default task list in Todoist. When you add a task, it goes straight to your Inbox unless you specify that the task goes into a project.
Moving a task from the Inbox to a project
Sometimes, when adding a task you may not be sure which project it belongs in -- don’t worry, just start by adding it to the Inbox.
Later on, you can drag and drop tasks right into a project of your choosing (Web, macOS, Windows) or edit the task and add it to a project by typing in # (All platforms).
Adding a new task directly to a project
Of course, if you already know which project a task belongs in, you can just skip the Inbox and add your task there directly. When creating a new task, send it to a project by typing in the symbol # immediately followed by the project name. Once you type #, you can also choose from a list of existing projects, or create an entirely new one:
Read more about the basics of organizing your projects.