Flickr is a social photo app and sharing service.
You take your photos, add a title and description, and upload the picture online.
Other users can search and comment on your images. Flickr also supports geo-tagging, so others can know exactly where you took your picture.
Connected to different people, even through your contacts' list, you can see a variety of different pictures.
The interface of Flickr is a little small and the quality of images differs depending on the Windows Phone being used. It is a nice photo app, but feels a little old next to newer photo sharing apps available.
Flickr is a decent photo sharing app and has a good community, but lacks options of newer photo apps.