Photos deleted

Hello,

I have been organizing my photos for years using the photos app on my macbook, organizing them in folders according to trip/date/etc. I recently backed up my photos externally and then deleted them from my phone to clear space. However, this also deleted them from my library on my computer. Why would this be the case? Why does everything I have need to be linked? Why can't I just keep my pictures on my computer but not on my phone? And is there anyway to recover these photos but only on my computer? Please advise if anyone has any idea how to fix this.

Thanks!