2004 bmw 525i

I got a code saying my PCM might need to be changed out for a new one or reprogrammed

The code was p16a7

But my thing is pcm the same as an ECU better yet is a PCM, ECU, and ECM all the same thing, or what cause I am confused about it

Or is a PCM a whole other thing on its Owen if so where can I get a new one, returned/ reprogrammed

Any help will be appreciated