When uploading a project to the site you can choose to make it private or public. 

A public project is included within the searchable directory of projects, it will show up in external searches and is linked to a public URL, it is also visible on your CC profile.  

A private project can be used for applications, won't be shown on your profile and isn't visible within any external search results. 

A private project can be made public and vice versa at any time by editing the project, switching the permissions and saving.