Lightroom does not store (or contain) your photos. In order to use Lightroom, your photos must be on a hard disk somewhere, in whatever location you want them to be in (your choice), so you can also find them with your operating system, and so Lightroom knows where to find them as well. There is a built-in tool in Lightroom 5.7 that will extract photos from Aperture and put them into whatever folder you choose for Lightroom to use and create the appropriate Lightroom catalog file.
Thank you dj_paige. I have only just started using Lightroom as you can see . I am reading over and over to really work through the manuals and tutorials, and it is beginning to sink in. I look forward to getting proficient soon.