Click tracking allows you to know whether or not your prospects click on the links in your emails.
You can enable or disable click tracking from Settings > Tracking:
Set up your own domain for URL Rewriting
In order to track clicks we rewrite all links included in your messages by a tracking URL. By default, we'll use a shared Prospect.io's domain but we strongly recommend you use your own domain in order to make sure your emails get delivered, as Email Service Providers tend to be suspicious about links not pointing to the sender's own domain.