What does the phrase mean - "to live is Christ and to die is gain"?

[Karmageddon]

“For to me, to live is Christ and to die is gain.”- Philippians 1:21

 

[hotcocoa1897]

you have to live for christ and wen you die you gain the kingdom of heaven!

 

[MreSpock]

It doesn't matter what happens to me. As long as I'm alive, Christ is living through me, which is awesome. And, when I die, I'll lose this world, but gain heaven, which is infinitely better. So, whether I live or die, I can be joyful.