These two people are fictional characters in sci-fi show called Torchwood, created by Russell T. Davies.
Many fans ship this pairing, but since Janto has gone canon, many have supported Janto instead.
'Jacken' is a joining of Jack's and Gwen's names; the 'Jack' from.. Jack, and the 'en' from Gwen.
Jack and Gwen have shared 2 kisses in the first series of Torchwood, in the episode 'Day One' and the other in the finale, 'End Of Days.'
'Awww, Jacken kiss.. *loves*'