Radios are portable communication devices which consist of low-power transmitters and receivers. Originally created for military purposes during the Second World War, they became popular again in the 70s with the CB radio craze. The most enthusiastic users of toy models were children looking for a way to talk to each other "in secret".
Radios are wireless, fit in one hand and small enough to be carried around everywhere. They are very similar to the wireless handsets with a body which has a microphone, a speaker and an antenna. Unlike the phone, however, the speaker and microphone of the Walkie talkie are located next to each other and the speaker is much more powerful, so anyone within the range in which the sound is heard can follow the conversation.
The radios are powered by batteries. They have a half-duplex channel, which means that only one radio can transmit a signal over a channel at a time, although many other radios can accept it. In other words, unlike your phone, in which both parties can simultaneously participate in the conversation, the radios have a push-to-talk system - you need to push a button to talk and need to release the button to hear the signal transmitted by the others.
On the other hand, radios are much faster and easier to use because you do not have to dial a number. Their best advantage is that they do not rely on cellular signals which may not be available. Handsets transmit directly to one another. That is why they continue working while cellular networks cease to function during natural disasters or power failure. They are designed mainly for communication over short distances.
Many employers use radios so as their employees can talk to each other within their business premises. Keen travellers use their radios when travelling to places where there is no mobile network coverage. Even baby monitors use the one-way technology of radios so as to make sure you can keep an eye on your little ones and check if they are sleeping peacefully or are about to get into mischief.