A/C with low speed fan means that when the humidity level is too high in your home the air conditioning will come on and run the fan in low speed to remove moisture
A/C with high speed fan means that when the humidity level is too high in your home the air conditioning will come on and run the fan in high speed to remove moisture
Whole house dehumidifier means that when the humidity level is too high in your home the whole house dehumidifier will be activated to remove moisture