Where on the file system are my photos imported to?
If you're using the Photos application then your imported pictures can be found at:

~/Pictures/Photos Library


This is a special folder. If you double click on it in Finder it'll open the Photos application instead of showing you the contents of the folder. To see the contents, right click on the folder in Finder and select Show Package Contents from the menu.

Once you're inside the special folder the unaltered master photos are in the Masters sub-directory sorted in to year and then month then day sub-folders.

If you're trying to find the path to the location from a Terminal command line it's:

~/Pictures/Photos Library.photoslibrary