Is my FTP login different from my WP login?

Hello,

I’m currently experiencing a problem with “500 Server Error” messages on my website. While I’d normally log in and fix it, I can’t do that, either.

So I’m attempting to connect to the server via Mac’s built in FTP. However, no matter what I try, it keeps telling me that my username/password is incorrect. Is the login different? Or am I putting entering the website into the “Server Address” section incorrectly?

I’ve tried:

ftp://www.MYDOMAIN.com/
ftp://MYDOMAIN.com/
ftp://www.MYDOMAIN.com/wp-admin
ftp://MYDOMAIN.com/wp-admin

Please let me know what I’m doing wrong. I need my site back up and running pronto.

Thanks