Double Dash
Used to signify the end of command options, after which only positional arguments are taken.
For example, you may want to create an odd file named -abc. touch -abc will not result in the creation of a new file named -abc, however. It will instead try to interpret the added -abc as a parameter option, which is contrary to what you want. To get around this, run touch -- -abc.
TLDR Cheat Sheet:
-- = Used to signify the end of command options.
> = Redirect stdout
1> = Redirect stdout (equivalent to above). The 1 is a file descriptor.
2> = Redirect stderr
>& = Redirect a stream to another file descriptor.
2>&1 = Redirect 2 (stderr) to 1 (stdout).
| = Pipe operator; pipe the output and pass that output as input for another command.
a & b = Run a in the background and run b in the current shell.
a && b = Run a. If a succeeds, run b.
a || b = Run a. If a fails, run b. (If a succeeds every time, b is never run.) . Not related to the pipe operator or |.
${var} = Expands a variable
$(cmd) = Evaluate a command inside the parentheses. Command substitution. The modern and preferred way of doing command substitution.
`something` = Everything inside the backtick is evaluated before. An older way of doing command substitution. This method doesn't allow you to nest expressions like $(cmd) can. Another caveat is that this method only substitutes the stdout, and not stderr.
WIP