It's stores up to a certain amount of photos(#GB). Once you reach the free limit, you can buy more space or it simply stores the latest 200 or so files on line. You're earlier uploads are still stored, you just can't access them, unless you buy more space.
I have no need of the online storage for my photo files. I keep the files (RAW images averaging about 20MB each) on a few external hard drives. They're pretty cheap these days so you can back up files safely.
I think the more important thing is the software you download your images - from your camera - onto your computer, Chris. I use Lightroom these days but used Iphoto for years. Your camera likely has it's own and those have been good too.
I store about the last 3-4 years of files on my power macbook's HD, that I upload from my Canon camera, into Lightroom(more take up too much storage space on it).
After I make adjustment to the images(usually includes sizing for the internet), I send them to a file on my desktop(photos - sized ). When I want to post an image, I open Flickr, click- upload, and choose the image. Flickr will up load any size(it has it's own limit it will set).
To post, I go to Flickr, and there the image. Click the 'share' icon - it shows and copies the link - go to CSBB and post the link - where I want it - in the body of the post. The only slow down is I have to remove some extraneous text on each side of .
It's so much simpler to do than explain, you'll be amazed. I'm glad your wife gave you that camera, we'll all benefit seeing more of your travels.