A couple of days ago, at the Annual Bloggers Bash in London, during my Q&A, I got asked about the difference between “Press This” and “Reblog”. Here a more extensive answer.
Press This provides a lightning-fast way to grab text, images, or video from any website and post it to your blog. It works with WordPress.com sites and self-hosted WordPress sites.
Press This is a bookmarklet, a special piece of code, that is saved as a favorite in you browser’s bookmarks bar and allow to perform a quick action, with just a click.
Reblog is a special feature of WordPress.com. Reblogging is a quick way to share posts published by other WordPress.com users on your own blog. To reblog a post, click the Share button from the Reader or the Reblog button at the bottom of a post directly on the site.
Here you can find all the information about Reblog on WordPress.com.