Opens a memory stream to write data to (you can then write that stream to a file stream using :writeStream)
how to open the file, w is write mode, a is append(and it will add to an existing file or start)
The compression type to use, anything that isn't store or none will have compression enabled
The compression level to use, 0 is terrible compression, 1 is fastest, 6 is balanced, 9 is best compression
If you want to skip the header, if you do you can't read the file without knowing the compression type