Silent Circle and Silent Phone and Silent World, oh my

 So what is Silent Circle and Silent Phone and Silent World?

Silent Circle:

 Silent Circle is the name of the company that offers these products.

Silent Phone:

Silent Phone is the main software offering from Silent Circle. It is an app that is available for Android, iOS.

Silent World:

Silent World, formerly known as "Out Of Circle" calling is a reference to a calling plan that allows calls to non-Silent Circle contacts using minutes or credits. All Monthly Credit Plans are considered Silent World as all monthly plans have the ability to call non-Silent Circle contacts by deducting the cost of the call directly from the credit balance. SW100, SW500 or SW1000 will deduct minutes from the monthly minute allowance for calls to non-Silent Circle contacts.