"Blower speed" refers to the rate at which air is pushed out by a blower or fan. It describes how fast or slow the fan is spinning to blow air or cool down an area. Full definition
As an example, my 2004 Honda CRV has air conditioning that is controlled by three controls: on / off button, blower speed knob, temperature knob. (mechanics.stackexchange.com)
Starts with blower speed control working inconsistently, then dash lights go on or off or light up like a Christmas tree and the vehicle may stall. (carsdesk.com)
I imagine the combination of on / off and blower speed engage a clutch in the compressor that can only engage / disengage. (mechanics.stackexchange.com)