likely flashbacks. As far as the cinematic universe is concerned, we know next to nothing about Kylo Ren's past, only the general gist. The makers seem very concerned about making Kylo Ren a "humanized" villian rather than all bad. I'm assuming we'll see some more interactions between Han and Kylo via memories, or at least Han, Leia, and Kylo as a family, before it all fell apart.