The shift level is locked by the shift solenoid. When you step on the brake, the brake switch sends power to the shift solenoid and it moves a lever to unlock the shifter. If either the switch or solenoid is bad, you can't shift out of park.
check the brake pedal switch
It could be mechanical or it could be electrical. Sometimes if you park on a steep incline or park hard up on a curb, the shift will be difficult to come out of park but it should with a little extra pull on the lever. Also, check the fuses. many vehicles today must have the brake pedal applied to release the shift lever from park. If the fuse is blown that protects that circuit, the shift lever will not move.
The cable between the shift lever and the transmission may be bad.
moving the shift lever from park to drive or any other position with the engine off will not hurt anything in the transmission. in an older automatic trans by moving the shifter from park to drive the shifter is mechanically atatched to a lever which is attached to a manual valve inside the transmission. since the engine is off there is no pressure in the transmission so nothing happens. on a newer auto trans the shifter is attached to a lever which moves electrical contacts to do the same thing as the old mechanical trans lever.
Simply start the vehicle with the shift lever in the Park position. If you wish to go backward place the shift lever in the R location. When you're ready to move forward place the shift lifter in the D position. Only shift from park to reverse or to drive when the vehicle is sitting still.
SOMETIMES IF THE STEERING WHEEL IS LOCKED YOU WONT BE ABLE TO SHIFT OUT OF PARK. TRY JIGGERING THE STEERING WHEEL AROUND.
CANT GET THE SHIFT LEVER OUT OF PARK
Step firmly on the brake pedal. Pull the shift lever toward you and down.
Check all the linkage from the transmission.
The cable/linkage between the shift lever and transmission is likely broken or disconnected
On a 1998 Ford Taurus ; On the column shift the overdrive button is on the end of the gear shift lever On the console shift the overdrive button is on the drivers side of the gear selector lever below the button you have to press to shift out of PARK