bat:tldr:90d1d

This command is using the bat command and three variables to redirect the contents of file1 and file2 to target_file.

Here's a breakdown of each element:

• bat is the name of the command being executed.
• ${file1} is the first variable. The command is expecting a file name or path as a value for this variable.
• ${file2} is the second variable. Similar to file1, it is expecting another file name or path.
• >> is the output redirection operator. It appends the output of the command to the specified file instead of displaying it on the screen. In this case, the output will be appended to target_file.
• ${target_file} is the third variable. Like the previous variables, it should be a file name or path.

So, running this command will take the content of file1 and file2, execute the bat command with those files as input, and append the output to target_file.