HF, or high frequency, refers to a range of electromagnetic waves with frequencies between 3 MHz and 30 MHz. This frequency range is commonly used in various forms of communication, including radio broadcasting and amateur radio. HF waves can travel long distances by reflecting off the ionosphere, making them ideal for international communication. In addition to communication, HF is also used in other applications such as aviation and maritime navigation. The ability of HF waves to cover vast distances allows for reliable connections in remote areas where other forms of communication may be limited.