The 802.11g/b WLAN USB (20) Adapter is a wireless network adapter that allows your computer to connect to Wi-Fi networks using the IEEE 802.11g and 802.11b standards. These are older Wi-Fi standards, with 802.11g supporting speeds up to 54 Mbps and 802.11b supporting speeds up to 11 Mbps. The "USB" part indicates that the adapter connects to your computer via a USB port. The "20" might be a part of the model number or a reference to a version or specific hardware revision.
To make the adapter work properly with your computer, you need to install the correct Windows driver. The driver enables Windows to communicate with the adapter, so it can detect available Wi-Fi networks and establish a wireless connection.
802.11g/b WLAN USB (20) Adapter Windows driver: