Timeline project
Timeline project is a folder in a Subversion repository that corresponds to one folder together with its contents on your computer.
The notion of Timeline project was introduced into Timeline because Timeline has to preserve folder hierarchy, i.e. when adding files to a project Timeline creates the same hierarchy of folders in the repository as on your computer. This is needed to facilitate synchronization of the files between your computer and the repository. Timeline always knows which file in the repository corresponds to some particular file on your computer, even if you have 2 or more files with the same name. Also, copying folder hierarchy from a computer to the server allows Timeline to recreate the same hierarchy on additional computers.
Practically, in order to copy folder hierarchy to the repository when creating a new project you need to select a folder that will be a top-level folder in this hierarchy. Please note that when you choose the top-level folder Timeline doesn't actually copy any files or folders - it just establishes mapping between the top-level folder in the project and a folder on your computer.