M.2 stands for Next Generation Form Factor which is invented for PCI-SIG by Intel and it is developed for flat and high-efficiency equipment such as Ultrabook™ or Tablet PCs. It is a natural transition from the Mini Card and Half Mini Card to a smaller form factor in both size and volume which supports multiple function add-in cards/modules including: Wi-Fi, Bluetooth, global navigation satellite systems, near field communication, Hybrid digital radio, wireless gigabit alliance (WiGig), wireless wide area network and solid-state storage devices. Also adds functionality to USB 3.0, display Port, SDIO and SSD-PCIe
The PCI-E M.2 Card passive adapter is designed for wireless application on desktop PCs that convert half-size MiniCard to USB 5pin Header or standard PCI-Express 1x slot.
You can insert your USB type M.2 card to this adapter then plug to USB 5pin header port through USB cable.
Or insert your PCI-E type M.2 card into this adapter then insert to PCI-E 1x connector.
Also, WiFi & Bluetooth Combo card such as Intel® Dual Band Wireless-AC 7260 can be used for supporting both WiFi by PCIe and Bluetooth by USB at the same time.