I have these fans in mind to use for my upcoming build. I checked their specifications and it says that they have three speed modes for performance, overclocking and turbo. I'm curious as to what turbo is?

I didn't realize that there was something MORE than overclocking. Another thing I wanna know is how would I set the fans to determine which speed type to use. It says that those fans have a speed controller switch on the fan hub to switch between speed types but I wouldn't wanna physically change between them but rather have my computer automatically adjust to one, like overclocking (and I'm assuming it's all done through the computer bios or something along those lines?)

Thanks.