Here's what each part of the description means:

MH-M18: This is the model or product identifier for the Bluetooth audio receiver board. It helps identify and differentiate this module from other similar devices.

Wireless Bluetooth Audio Receiver: This module is designed to receive audio signals wirelessly via Bluetooth. It can be paired with Bluetooth-enabled devices such as smartphones, tablets, or computers to stream audio content to an external audio output.

Board Module: It's a standalone circuit board with all the necessary components and connectors for its operation. You may need to integrate it into your project or connect it to other audio equipment.

BLT 4.2: This indicates that the module uses Bluetooth version 4.2 for wireless communication. Bluetooth 4.2 offers improved data transfer rates and lower power consumption compared to previous versions.

mp3 Lossless Decode: The module is capable of decoding and playing audio in the mp3 format without significant loss in audio quality. "Lossless decode" suggests that it can reproduce the audio with high fidelity.