How to rename a CSV file by adding MODIFIED in the filename?

[Python_User]

What does this part of the code below? Could you provide some explanation behind the lines of code as comments?

def read_csv_file(filename):
    parts = list(filename.parts)
    parts[-1] = f"{filename.stem}_Modified{filename.suffix}"
    parts[0] = ''
    outfilename = Path(f"{'/'.join(parts)}")
 
    print(f"new output file name: {outfilename}")
 
    with filename.open() as fp, outfilename.open('w') as fout:
        crdr = csv.reader(fp, delimiter=',')
        cwrtr = csv.writer(fout, delimiter=',')
        for row in crdr:
            print(row)
            # Modify row as desired here
            cwrtr.writerow(row)