WiFi module says "mini PCI-e format" with "USB host interface" - what does this mean?
The statement:


Host interface supports USB.2.0 Works with any board with mini PCIe.


Means:


The card in question physically interfaces via a PCIe "socket".
One of the connections which can be established over this connector is USB2. The USB data lines are usually on pins 36 &amp; 38 of the connector, BUT they are not present in some implementations and if someone put USB on some other pins in a particular implementation you shopuld not be completely surprisd - BUT, it probably means it uses  USB2 on PCI-e pins 36 &amp; 38. 


The situation is confused by there being various sub-implementations or semi-non-standard or very non standard implementations. Note that when eg SATA is used the USB pins are "reserved" implying that you MAY in some cases be able totalk to a drive via SATA or USB2. 

USB data is usually carried on pins 36 and 38 BUT no absolute guarantees.

This webpage does a fair job of showing standard and some non standard implementations
 Clearer version on webpage. 



Wikipedia on PCI express says
as below, which covers the USB2 part of your query.


PCI Express Mini Card edge connector provide multiple connections and buses:

PCIe ×1
USB 2.0
SMBus
Wires to diagnostics LEDs for wireless network (i.e., Wi-Fi) status on computer's chassis
SIM card for GSM and WCDMA applications. (UIM signals on spec)
Future extension for another PCIe lane
1.5 and 3.3 volt power)


A typical PCI-e wireless LAN card whose webpage contains the search string you ask about has the picture below. And includes text


Host Interface supports USB 2.0 via mini PCIe format.


and


Works with any board equipped with mini PCIe.


"via mini PCIe" and "equipped with mini PCIe" tell you that this is NOT an alternative to USB2. 

That pretty much covers the PCI-e aspect of your query.





Many bus pinouts excellent

Including PCI-e

Excellent PCI-e resource page



Gargoyling


Host interface supports USB.2.0 Works with any board with mini PCIe.


produces a slew of material with that exact string, and many that answer your questions and various explanatory material as well.