This is a split 7z archive file . The ".001" indicates it is the first file in a series.
You cannot extract the photos from just the .001 file alone; you need the entire set. If you are having trouble opening it, I can help you with: Wedding Pictures.7z.001
To open this, you must have all subsequent files (e.g., Wedding Pictures.7z.002 , Wedding Pictures.7z.003 , etc.) in the same folder as Wedding Pictures.7z.001 [7-Zip FAQ]. How to open it: This is a split 7z archive file