39A ejector/extractor

I still have problems after sending my 2 year old 39A to 2 gunsmiths. They replaced the inner tube, outer tube and the cartridge guide spring. The gun ejects 3-4 rounds then it takes another 4-5 ***** and they start coming out again and so on. I have a new Wisner extractor for it and will get another smith to install. I have read the stickies about this and the extractor sounds like what I need. The question is.......what is the difference between an extractor and an ejector and their functions?