"The photo sphere camera mode on your Android phone makes it easy to capture a series of photos and automatically turn them into a seamless 360º experience. You can also turn your DSLR camera panoramas into photo spheres," explains Google. This page has more information about the photo sphere mode and about creating panoramic images manually.
Google Maps Views has a camera button that lets you add photos from Google+. You can also use Android's share feature and share a photo from the gallery with Google Maps, so that it's quickly uploaded. Google creates a page like this one with all your photo spheres.
Google Maps Views showcases popular photo spheres and some special Street View collections, including landmarks (Eiffel Tower), natural wonders (Grand Canyon), museums, arenas, restaurants and small businesses. You can also use the search box and find a list of popular photos and top photographers for that location.
Photos spheres don't replace Street View, they only complement Street View with a fun, fresh and personal perspective that captures the the world around you.