Recently SkyDrive changed its name because of some copyright issues to OneDrive and is finally live now (OneDrive is live since 19 of February). I'm pretty sure you have your stuff in same way as it was in SkyDrive. SkyDrive used to give 7GB for free to all users and OneDrive is doing the same but it is also offering some more as bonus space.
OneDrive gives you 3GB for activating camera backup feature which is available in Android, iOS and Windows Phone applications. Technically, Microsoft is offering you free storage if you agree to store your images or videos on their OneDrive. Other 5GB can be claimed by referring friends to OneDrive. You can refer 10 friends which will cover you 5GB extra storage (500MB for each person you refer).
If you get extra 8GB then you'll have 15GB of free storage from SkyDrive. Do you know Google Drive is also giving away free 15GB of storage to everyone? I'm sure you know, but do you know it is shared between Gmail, Google photos and Google Drive.
7GB free + 8GB extra (also free) = 15GB of free storage