SSL certificates are a very important part of the internet. These certificates allow encrypted communication between your browser and https://zapier.com. They also allow your browser to guarantee you're actually looking at the webpage we intended. Both of these details prevent would-be attackers from snooping on your private browsing or business data.
SSL certificates are also widely used when dealing with APIs. The same technology that lets your computer's browser talk securely to https://zapier.com also allows Zapier to talk securely to other web services (like Gmail, Salesforce, or Zendesk) in order to access your data on your behalf.
In order for SSL certificates to work, both parties (ie. your browser and https://zapier.com) must "trust" an independent third-party, known as a Certificate Authority (CA), who signs every SSL certificate they issue.
There are hundreds of CAs on the internet. In fact, for SSL to work properly, the list of CAs both parties "trust" must be continually updated an onerous detail.
You can find a list of the CAs we trust here.