Could be any of literally dozens. In some cases even locations play into what frequencies may be used. For example some Walkie Talkies here in the US use the Citizens Band in the 27 MHz neighborhood while others use FRS (Family Radio Service) bands up around 462 to 467 MHz. Those are just two examples applicable to the US.
Europe has something similar to the FRS but it is called PMR (Private Mobile Radio) with other frequency allocations. You can likely Google the latter for frequency information.