Rotary dialing was used on older telephone systems.
When a number is selected, it made that many clicks onto the phone line. For example ‘3’ would make 3 clicks, ‘9’ would make 9 clicks, etc.
While most rotary phones have disappeared, their clicking function hasn’t. A “pulse” option is still present on most landline phones. “Pulse” emulates the rotary sound, and is an alternative to the “tone” method used by most phones.