Walkie-talkies, as they were called, were first developed for military use during World War II and eventually spread to public and commercial use after the war. They typically look like a telephone handset with an antenna sticking out the top with a built in speaker that can be heard by the user and anyone in close proximity.
Modern walkie talkies still utilize the push-to-talk technology and are available in numerous price ranges - from units sold as toys to more commercial units used for public safety, business or any setting where a portable radio would be necessary. Some walkie talkie models can be made to be very small and depending on the differing use, the equipment varies with consumer use and commercial use.
Commercial walkie talkies - also called commercial two way radios - have a more rugged construction with metal cases, and often have only a few specific frequencies programmed into them since a given business or public safety agent must often abide by a specific frequency allocation.