"What does it Mean?"

But what does it mean?
It means they have the ability see every website you visit, every text message you send, every call you make, every ticket you purchase, every donation you make, and every book you order online. From “I’m headed to church” to “I hate my boss” to “She’s in the hospital,” the GCSB is there. Your words are intercepted, stored, and analyzed by algorithms long before they’re ever read by your intended recipient.

Faced with reasonable doubts, ask yourself just what it is that stands between these most deeply personal communications and the governments of not just in New Zealand, but also the U.S., Canada, the U.K., and Australia?
...
The answer is that solitary checkbox, the Five Eyes Defeat. One checkbox is what separates our most sacred rights from the graveyard of lost liberty. When an officer of the government wants to know everything about everyone in their society, they don’t even have to make a technical change. They simply uncheck the box. The question before us is no longer “why was this done without the consent and debate of the people of this country,” but “what are we going to do about it?"

Edward Snowden on  Five Eyes Surveillance on The Intercept