Article submission is writing articles for submission to publications and sites. You hope to get it picked up and re-published since it should contain a hyperlink (backlink) to your site, boosting your reputation with Search Engines.
There are various submission sites and many submit to lots of them. There are services that do it for you for a fee since it is time intensive. The trick is to not duplicate your copy if you submit to multiple sites. Software is available to help you do this. Or you can use an Excel or OpenOffice spreadsheet to assist.
Blogging is writing articles on your own Blog site. Can be the same topics as above. Again, avoid duplicate content by making your blog site the original post. Blogs are not solely text, however. You can add photos, videos, podcasts, etc.