What is the script or plugin? Very cool...

I’m looking for a particular script found on a website but I can’t seem
to name it. See the script here twolittlefleas.co.uk/bingo-guides/
What powers that little pop-up offer with the envelope on the bottom
right (with the offers)? Is it some kind of wordpress plugin or
javascript? How can I replicate it for my website? Please recommend a
script or preferably a wordpress plugin that has this functionality.