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.
A project is a task list that you create yourself. You give a project a name and then start adding tasks. You can also set a project’s color or share projects with your teammates.
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 the task right into a project of your choosing (Web, macOS, Windows) or edit the task and add it to a project by typing # in the name field (all platforms).
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.
If you're new to Todoist and want to get up to speed quickly about the basics, check out this video to help you get started.