Help understanding (new)

Let me start by saying thanks for any help at all. the problem i am having is understanding using a function how to call a function to gather data from a file, have the file accept the good data and put the bad data in error file. The catch is we have to use a void function using ampersand. This is what i got so far but kind of hit a wall. Any help would be great, i am trying to hard to learn and understand what is taking place.
Help understanding (new)