Fromman bash:

-- A-- signals the end of options and disables further option processing. Any arguments after the-- are treated as
filenames and arguments. An argument of- is equivalent to--.

In other words,-- is used to signify theend of command options. After it, only positional parameters are accepted.

For example, we want to look for the "--color" string usinggrep:

$echo"hello --color" |grep--colorusage:grep[-abcDEFGHhIiJLlmnOoqRSsUVvwxZ][-A num][-B num][-C[num]][-e pattern][-f file][--binary-files=value][--color=when][--context[=num]][--directories=action][--label][--line-buffered][--null][pattern][file ...]

We got an error, since--color expect a value. We can fix by signaling the end of options to the grep command using--:

$echo"hello --color" |grep----colorhello--color

It's important to note that not all bash builtin commands accept the-- as an end-of-options marker.