zmv:tldr:d11bc

The command is written in the zsh shell and uses the zmv function to rename files.

Here is the breakdown of each part of the command:

1. zmv: zmv is a built-in function in zsh shell used for batch renaming of files.

2. '$': The dollar sign indicates the start of a parameter expansion. It is used to reference the positional parameters in the form of $1, $2, etc.

3. ${(*)-log}: In zsh, ${(*)} expands to all command-line arguments passed to the current script, while ${(*):-log} expands to the first command-line argument if available, or log if no arguments are provided. This is used to select the files to be renamed. So, all files matching the pattern -log will be affected.

4. '${$1-txt}': ${$1} expands to the first command-line argument, and 'txt' is appended to it. This means that the -log extension in the filenames will be replaced with the .txt extension.

To summarize, the command renames all files ending with -log by replacing the -log extension with .txt.