If you are asking about the "Library" view in Photos 5.0 (with Years, Months, Days, All Photos) or "Photos" view with "Years, Collections, Moments" in the earlier versions of Photos, it is not possible to remove photos from showing there, unless you delete them from the library or hide them as Tony pointed out. The Library view is by definition showing you all photos. It is the basic structure of your library and you are supposed to build your own structure on top of this with albums, smart albums, and folders.
If you need an album, where you can see all photos that have not yet been added to an album and need organising, create a smart album:
- File > New Smart Album
- Set the rule to "Album is not Any".
You will find all photos there, that have not been added to an album.