It could be someone who gets together with a love interest, but there’s no firm commitment like a marriage or mating contract.
It could be that whatever the Big Problem was has been resolved, and for the time being, at least, the MCs aren’t in any danger or at risk, and can canoodle happily until life rears its head and something nasty appears again.
For most publishers, they would say it means the characters are happy at the end of the novel without any assurance that the happiness is going to last forever.