It means that Hamas has children stand guard around rocket launchers. As far back as a decade ago, when this started becoming more and more common, I saved a video of a Hamas rocket fuse failing, killing the children guarding it. That was quite when I started taking more of an interest in what is going on over there.
The human shields are Gazan citizens - many of which are themselves happy to die "for the resistance" thanks to UNRWA education. This I have been told at least twice by Gazans face to face, and dozens of times online. Yes, I know Gazans and I speak with them online in Arabic. I suffer a lot of abuse, I have a thick skin (I laugh that I'm divorced, you can't insult me more than my ex).
There is no euphemism. These are real people risking their lives - and sometimes loosing - to protect military equipment designed to exterminate Jews. That is not a euphemism either - even the Gazans who work in Israel clearly state that all Gazans would happily kill any Jew. Just a few weeks before the October attacks I was having a conversation, pleasant and civil, and the guy tells me "without your weapons the Arabs would trample you" - I was unsure if he was threatening me. Just a few weeks after that they overran the Kibbutz where I until recently worked, and killed over 10% of the population. That is literal, biblical, decimation.