Inside the Blog article editor, on the top right, you can see that there is a toggle button called 'Draft'.
This basically indicates the published/ unpublished status of the blog article. By default, when you create a new article, it is ON. This means that whatever changes you make to the blog are in draft mode and are not visible on the public blog link.
Once you have finished writing the blog article and you are ready to publish it (i.e., make it public), turn the Draft mode to OFF. This will publish the blog article to the public blog URL.
When you want to make changes to a published blog article, first turn ON the Draft mode to unpublish the article and then make the necessary changes. Once all the changes are done, then turn the Draft back to OFF.
If you make changes to a published article with the Draft mode as OFF, the changes will be visible on the public URL as you edit.
