These are 3rd party apps and Web services that are connected to your data on social networks and cloud storage services. In some cases you may not be aware of this, or maybe you gave permission to such apps to access your data and forgot about it.
The “Connected apps” function of PlusPrivacy discovers all the apps connected to your Google, Facebook, LinkedIn, Twitter and Dropbox accounts, shows them to you and allows you to cancel access for each of such apps in a single click, from the Dashboard.