This is a wireless lavalier microphone set, which is mainly used to record clear voice or audio on a mobile phone or computer.
2 Clip-on Microphones (Transmitters): Which are used by clipping them to your shirt while speaking.
1 Receiver: The middle part, which contains various pins such as Lightning (for iPhone), Type-C (for Android), and a 3.5mm AUX jack, to be plugged into your phone or device for use.