2004 Honda Accord rocker arm actuator

Engine Mechanical problem
2004 Honda Accord 4 cyl Automatic 88000, miles

the computer read out said that the Rocker Arm Actuator A-Bank 1 stuck on. Computer number read out: P2647 I want to know what this means and a quess-a-mation of what this is going to cost me. The people at Auto zone were freaked out and wanted me to go trade my car in that night. Everyone says it is going to be very expensive and there seems to be this great secert with getting the parts. I want to know what this part does, and how it works so when I go and talk to a mechanic I will sound like I know what I am talking about. I do not want to get ripped off because I am a woman. To me it sounds like and electrical part going to the rocker arm on the engine and the lack of eletrial current getting to the rocker arm it has gotting stuck causing the engine to miss fire reducing the power etc. Please help. Sounds like and expensive fix to me?