A parenting magazine cover, in a Japanese supermarket: "子どもとのスキンシップが大事".
An English speaker reads it and their eyebrows travel a considerable distance.
It means: physical affection with your children matters. Hold them. That is the whole article.
The word appears in Japan around the 1950s and 60s, apparently coined in English-language parenting discourse and then adopted here permanently after everyone else quietly dropped it. It spread to Korean too, where it is equally standard.
It covers hugging children, holding a friend's arm, a parent and child in the bath together — which is normal family life here and startles some visitors — and casual physical closeness in general.
The reason Japan needed the word is that it is not, publicly, a touching culture. There is no cheek-kissing, no back-slapping, minimal hugging between adults. So the affectionate touching that does exist happens inside the family, and it got its own label precisely because it is marked off from everything else.
Cultures that touch constantly do not need a word for touching. It is like water for fish. Japan needed one — which tells you both that public physical contact here is rare, and that people considered its absence a problem worth naming and prescribing. The existence of this slightly ridiculous word is evidence of a country arguing with itself about affection, in print, since 1960.