what's eval code means ?

Hi Ya ....

   I just came back to AS400 world,  I am really lost in coding :-(    I saw eval  coding in RPG ...I just wonder what's that mean ?  is mean MOVE  from FieldA  to FieldB  ?              eval    FieldB         FieldB    

   I tried to move QDATE  into my display screen field   6 characters ....It's felt ....is anyone help me coding  in CL pleaseeeeee ....

  Thanks Alot