Meaning of "$" in .htaccess

.htaccess uses regular expressions for the settings. The $ character is an anchor to delimit the end of the string entered or until the \n line break. Its opposite is the ^ character, which will match the occurrence of the start of string or line.

For example, the following expression:

• [0-9]$ : Look for the digits between 0 and 90 that are at the end of a string or line

Using ^ :

• ^[0-9]$ : Search only the string or line that starts and ends with a digit between 0 and 9

From the documentation:

  

.htaccess files (or "distributed configuration files") provide a means of making changes to per-directory settings. A file, containing one or more configuration directives, is placed in a particular directory, and the guidelines apply to that directory and all its subsequent subdirectories.

Perhaps the apache documentation further clarifies the concept: link