Almost all blowers have three speads but are manually wired for only one at a time. They are commonly wired for medium speed. High speed cools faster, saves electricity but removes less moister. Low speed runs quieter and removes more moister.
Here in Florida most A/C guys just set it for medium due to the high humidity. In most blowers it's just a matter of changing a jumper wire coming of the fan motor (L2 wire side). You can also add a switch that will allow you to manually change speeds without opening the blower each time. My rentals and my home I set on medium because I don't want any mold problems.