PCI-E Wi-Fi adapters
PCI-E
— one of the interfaces used in internal type adapters.All such adapters are placed in slots on the motherboard; external connectors and antennas, if any, are output to the rear panel of the case (similar to how it is implemented, for example, in separate video cards and audio cards). Installing inside a PC case is perfect for those cases when the adapter is needed for permanent use and it is not planned to reconnect it. Specifically, PCI-E is one of the most common interfaces nowadays for connecting internal peripherals. It is widely used in modern motherboards (even small "motherboards" most often have several of these slots), which is why it is also popular among Wi-Fi adapters. Connection according to this standard can provide a different number of lines, however, in wireless adapters, PCI-E 1x connectors are most often used, suitable for slots with any number of lines (1x, and 4x, and even 16x). And the data exchange speed depends both on the number of lines and on the PCI-E version — however, it is usually not lower than 1 Gbps, which is more than enough in this case.
It should be noted that this type of connection is found mainly in adapters based on full-size boards; such modules usually have fairly powerful transmitters, and often also external antennas or connectors for such antennas. In miniature solutions with internal antennas, M.2 connection is becoming increasingly popular (see the relevant paragraph).