How do I edit the "Share this" text? What is it for?

Hello,

[1] I'm not sure what the "Share this" text is for and I don't see any way to edit it in the Settings area.

[2] How do I remove this text if I want to?

See image at link:

http://amson.org/images/share-this-june-14-1.png

Thank you,
Chris.