Thank you, Terence, for the information. I'm going to mull this over because what you have mentioned is rather abstract to my diminishing grey cells. When I returned to iPhoto, in the Photos' List, the photos I had categorized were in tact and none of the other photos were included.
Much for me to consider when importing photos and my placing them into folders but forget about 'trashing' what is in the Import file, because as you say, this is only a shortcut.
Again, thanks for shedding some light on my dimly lit understanding of iPhoto and its importing photos.