'Leads' in our reports and goals refer to visits to the client's web pages that contain our 'Lead' tracking pixel. We provide this pixel in Account Preferences.
You can position this pixel on Thank You confirmation pages wherever you determine a 'Lead' conversion takes place. It varies with every company.
For instance, some consider an eNewsletter signup a Lead, in which case they would place the pixel there. Others don't consider that a Lead, hence they wouldn't place the Lead pixel there.
Remarkably, you can place multiple pixels on one page.
As an example, you might want to create a custom tracking event for eNewsletter and place both the custom pixel AND the Lead pixel. By doing this, these events and other Lead conversion events are counted towards the company's total Lead count in reports.