RTL-SDR stands for "RTL Software Defined Radio." It is a low-cost USB device that allows users to receive a wide range of radio signals. Originally designed for digital television reception, it has been repurposed by hobbyists and professionals to explore various frequencies, including FM radio, weather satellites, and even aircraft communications. The device works by converting radio signals into digital data that can be processed by a computer. Users can utilize software applications to analyze and demodulate these signals, making RTL-SDR a popular tool for learning about radio technology and experimenting with different types of communication.