Some contents and information must appear at different places of blog or web site,
you need to copy/paste and duplicate contents, “Reusable Contents” helps you to control all in one place.
The idea of this plugin is like signature at the end of emails.
You can create any contents that includes images, HTML, shortcodes or event other “Reusable Contents”,… and reuse them (by generated shortcode) in in posts, pages, widgets,…
It saves you a lot of times by managing resuable contents.
You can export “Reusable Contents” by using WordPress Export and Import options.

suggested uages:

Announcements
Information
Advertisements
Testimonials
Contact information
Post Signatures
HTML, CSS, Javascript block of code