A {@link org.netbeans.api.project.Project} is a representation of a folder which may contain various kinds of development artifacts and/or metadata. Projects can be loaded, saved, etc. using {@link org.netbeans.api.project.ProjectManager}.
{@link org.netbeans.api.project.FileOwnerQuery} is a simple way to associate a file or folder with a project. Typically, all files beneath a project's folder are considered "owned" by that project. A given file can be owned by at most one project.