What is this?

This is a URL shortener. Sometimes super long links can break in emails, and some services like Twitter require you to keep your links as short as possible. This service lets you take any link and make it tinier and easier to send.

I'm worried about security.

You can aways preview the destination of a link before clicking it, just add /pr/ before the identifier. As an example, http://www.cuturl.co.uk/123a would become http://www.cuturl.co.uk/pr/123a.