What are "-" (one dash) and "--" (double dash) used for in the unix shell?

Question

Command line

Explain in plain language what is "-" (one dash) and "--" (double dash) in commands? What's the difference between them?

Answer 1

There is a rule: if the parameter is one-letter, then a single dash is used, and if it is longer (a word), then a double dash is used. But this rule is not observed everywhere.
In some commands, a double dash means stop processing input parameters.
Another single dash usually serves as an indicator that standard input (stdin) is being used instead of a file.
But at the same time, this cd -is a transition to the previous directory.