The following is an excerpt from iw's help page:
dev <devname> set monitor *
Set monitor flags. Valid flags are:
none: no special flags
fcsfail: show frames with FCS errors
control: show control frames
otherbss: show frames from other BSSes
cook: use cooked mode
active: use active mode (ACK incoming unicast packets)
mumimo-groupid : use MUMIMO according to a group id
mumimo-follow-mac : use MUMIMO according to a MAC address
What is "cooked mode" wifi monitoring?