Ethernet over Wireless Question

Hi,
I have a general question with wireless ad hoc transmission.

I wrote a code that does simple data transmissions using raw ethernet
over wireless 802.11 between two devices.
I manually construct the ethernet header and set the dest/source MAC
address before I send the frame using sendto(2).

I notice that the header for 802.11 packet is different from the
ethernet header. So does the ethernet frame being encapsulated over a
802.11 frame? or is it being converted to 802.11 header?

I'm assuming the driver is doing all this, correct me if I'm wrong???

Does it do it selectively? meaning if I constructed 802.11 frame and
sending it via sendto(2), would it still encapsulate/convert the frame
onto another 802.11 frame, or would it detect that it's already a 802.11
frame so it just sends it ie. saves speed?

Thanks.

-Stefanus