Walkie-talkie was originally the name Motorola gave to one of its handheld radio lines. Eventually it became a standard term describing most any handheld radio that lets you receive and transmit. Kinda like Kleenex or Q-tip.
He most likely got dual GMRS/FRS radios. The difference is mildly confusing, but mostly comes down to how much power you can transmit with which loosely correlates to how far apart they’ll work.
FRS stands for “Family Radio System”, and transmits on 14 channels on fairly low power (giving a range of about a mile). Anyone in the US can use FRS channels without a license.
GMRS stands for “General Mobile Radio Service” and uses 22 channels, most of which are shared with FRS. It lets you transmit at higher power, and gives a range of about 5 miles, depending on conditions. You do need to get a license from the FCC to use GMRS.
Most of the GMRS/FRS radios out there only let you transmit on the FRS channels at low power, or need to be manually set to high power. They’ll still let you use the GRMS channels without the license, though.
I don’t know if you’ll get in trouble using GMRS frequencies without a license, but I’d suggest either telling the kid not to go over channel 14, buying the license, or returning them and getting cheaper FRS only radios that you’ll feel less bad about when the kid loses interest in them. The license is $75 for 5 years. You never know when the FCC will get a bug up their butt about enforcing something.