I have a 2000 Corvette and the Check Engine light came on, power was decreased and it said check Active Handling System...what does this mean and what kind of problems does it create?

There is a lot involved here ,you'll be better off if you take this to a Chevy dealer . They have the factory training an diagnostic tools to check this !Or a good ASE certified repair facility ! The Active Handling System is part of the ABS - antilock brakes ! The control modules on this vehicle are intertwined on a class 2 serial data communication network ! The active handling has or had a malfunction an informed the engine computer ,so the engine computer reduced engine power an retarded engine timing !
The Brake Pressure Modulator Valve (BPMV) provides brake fluid modulation for each of the individual wheel circuits as required during an Antilock, Traction Control, or Active Handling (RPO JL4) event. During the Antilock mode, the BPMV can maintain or reduce brake fluid pressure independent of the pressure generated in the master cylinder. The BPMV does not provide more pressure than is applied by the master cylinder during an Antilock brake event. During a Traction Control or an Active Handling event the BPMV applies pressure independent of the master cylinder to the individual wheel circuits.
The EBCM continuously checks the speed of each wheel to determine if any wheel is beginning to slip. If a wheel slip tendency is detected, the EBCM commands appropriate valve positions to modulate brake fluid pressure in some or all of the hydraulic circuits to prevent wheel slip and provide optimum braking. The EBCM continues to control pressure in individual hydraulic circuits until a slipping tendency is no longer present. If equipped with Active Handling the EBCM also monitors the yaw rate error. If the yaw rate error becomes too large, the EBCM will modulate brake fluid pressure to the individual wheel brakes as needed to restore the proper yaw rate error. If the EBCM detects a system malfunction, it can disable the Antilock, Traction Control, and Active Handling functions and turn on the Antilock and/or Car Icon (TCS indicator) Indicators in the instrument cluster.

Have the codes checked. There are to many possibilities for your car to list. Repost with the codes. Kind of problems it creates is lost power and handling.