The 41MP sensor of Lumia Camera enables you to take sharp photos. When you take a photo, the camera saves 2 versions of it: a full-resolution photo (34MP), and a high-resolution photo (5MP). The full-resolution photo can only be viewed in Lumia Camera, where you can also zoom and reframe this detailed photo. Elsewhere, for example in Photos hub, a very clear 5MP version of the photo is used. This 5MP version of the photo is easy to share, for example, in social media.
Note: Technical info about pixels applies only to Lumia Camera in the Lumia 1020.