With these commands if your .iso or other download is interrupted by something in the internet it will automatically resume. Also if the download is interrupted by a power outage one can resume the download exactly where it left off. The aria2c command is preferred for .iso downloads.
Some URLs redirect to some other sites. This option tells cURL to obtain the file from that redirected location.
-C –
This option is for telling cURL to resume download and the dash ("-") that follows it is to automatically detect the size of the file to continue downloading.
This option will make aria2c retry downloads for unlimited times. Some servers tend to break connection after some time. But, this option makes aria2c to auto retry when such things happen.