zsh PS1, dollar sign in the beginning, why?
 

Here's the prompt for zsh:
Found somewhere that "$" before quotes. What does it do? Do I really need this "$" after "="?

$'string' is a quoting pattern that will evaluate any baskslash-escaped characters it encloses into their literal equivalents. It's similar in function to echo -e (at least in bash, not sure about zsh), except that it can also be used in places other than just echoing text.

$'\t' evaluates to a literal tab character, for example.

I've located the zsh user guide section concerning it:
http://zsh.sourceforge.net/Guide/zshguide05.html#l115