Each time you send an email through Pathway, an invisible pixel is added to your emails that is unique for each email you send out. Once your client opens an email, the tiny pixel is downloaded and we record it as one view, which you can then see in your reporting page. If your contact forwards your email and they open the forwarded email, that is also counted as one view under the contact that forwarded your email.
The tracking pixel is the industry standard for tracking open rates. However, there are some limitations with using this method. While it does give you real data in most cases, sometimes, some email clients do not allow images to show automatically. For example, when you open emails on an iPhone, this tiny pixel is automatically tracked. But, Gmail could have some limitations, so in reality, you most likely have more views than the reporting shows due to this technology limitation.