Amazon KDP allows you publish ebooks while CreateSpace allows you publish paperbacks. Both companies are owned by Amazon.
Today, a new trend is emerging that will make Amazon KDP a one stop shop for all things publishing. I would like to call it KDP POD as there isn't an official name for it yet.
KDP POD from my experience will come to replace CreateSpace eventually. At the moment, the company will work through all the bugs and the customer experience, and then one day, when they are ready, they will put CreateSpace out to pasture.
In my sincere opinion, if you want to do any publishing, use KDP POD because you are better off growing with the platform.
Have a great weekend.