What does the added "s' mean in an iPhone generation?

Question

I am a bit confused on the meaning of "s" in my iPhone 6. Kindly shed the light on this

Answer 1

 S in 3GS stood for "speed", based on how much faster it was than the 3G. Fans also sometimes make up their own meanings for what the s stands for: iPhone 4s: Siri. iPhone 5s: Security (for TouchID)