axel:tldr:3c75d

The command "axel -n ${connections_num} ${url}" is used to initiate a parallel download using the program "axel". Here is a breakdown of the different components:

• "axel" is a command-line download accelerator that allows multiple connections to a server to speed up the download process.
• "-n" is an option followed by ${connections_num}, which represents the number of connections (parallel threads) the download will use. ${connections_num} is a placeholder that should be replaced with an actual numeric value.
• ${url} represents the URL (Uniform Resource Locator) or web address of the file that you want to download. ${url} is also a placeholder that should be replaced with the actual URL of the file.

Overall, the command is telling "axel" to download a file from the specified URL, using a certain number of parallel connections to speed up the process.