World Band Radios are those radios that are capable of tuning into radio programs generated by, say the British BBC, Radio Australia(Australian ABC Radio programs), Voice of America, Radio Vatican, etc. These programs are transmitted on a regular weekly basis in any one 24 hour period. It is generally preferable to use 24 hour time, linked to GMT (Greenwich Mean Time) which is the time it is in London (UK) so that confusion is eliminated as when the program is broadcast. There are dozens and dozens of programs from countries all over the world in the special languages of these countries. For example if you are an Australian citizen but originally from Greece, you can tune into stations that enable you to keep your knowledge of the language up to date. The stations typically have a lot of local news which you would normally not hear. The World Band stations are generally broadcast in several frequencies at the same time, typically between about 1.8MHz & 29.00 MHz, especially between7 & 21MHz. You can look up the broadcasting details on Google etc. Phase-Locked Loop (PLL) is a circuit configuration invented over 80 years ago. Originally the circuit was so complex that it only appeared in expensive radios. With modern microchip technology, the PLL got a lot cheaper. The benefits of PLL technology enabled receivers to remain on a station frequency with great accuracy. The radio circuit did not ‘drift.’ PLL technology, though still not cheap, is a hallmark of quality short wave radios and that’s why Jaycar specifies them.