You follow the prompts to create a blog. You can save/preview/edit...as many times as you like. If you are happy with your blog and want it to go public, you click on 'publish this blog' (or something like that). If you never hit the 'publish' key, it stays in private just for your eyes.
I have lots of entries that are public. I have a bunch that's not published as they are just notes for me/myself/and I. Might be photos I grabbed from the internet to use as inspiration to do a project or a recipe idea that I am inventing.
Oh, and if you accidentally hit publish you can just as quickly un-publish it. Just one more click. Hope this helps.
Oh, I should say that my daughter tried to explain to me that there are ways to keep notes on my computer but when I do it her way...the notes are lost forever. Having everything handy here on NGA, a place I visit almost every day, things just don't get lost.