zstd:tldr:af1a2

The command "zstd --ultra -${level} ${filename}" is used to compress a file using the Zstandard compression algorithm, with a specific compression level.

Here's an explanation of the command:

• "zstd" is the name of the command-line utility for Zstandard compression.
• "--ultra" is an option used to enable the ultra compression level. Ultra level provides higher compression ratios at the cost of increased compression and decompression times.
• "-${level}" is a placeholder for the compression level parameter. The "${level}" indicates that the value for the compression level should be provided when executing the command. The actual value for "${level}" can be a number from 1 to 22, where 1 is the fastest compression with the lowest ratio, and 22 is the slowest compression with the highest ratio.
• "${filename}" is a placeholder for the name of the file you want to compress. The actual filename should be provided when executing the command.

In summary, this command compresses a file using Zstandard with a specific compression level (provided as a parameter), and the ultra option is enabled to prioritize higher compression ratios.