Features and usage are summarized on the homepage.
This script will prompt for confirmation before it does anything:
ruby -e "$(curl -fsS http://gist.github.com/raw/323731/install_homebrew.rb)"
Afterwards, install Xcode.
Indeed, you can. Refer to our complete installation instructions.
Okay then, but please note this installs Homebrew as root and we recommend against that.
curl -LsSf http://github.com/mxcl/homebrew/tarball/master | sudo tar xvz -C/usr/local --strip 1
The wiki is your friend.
I'm Max Howell and I'm a splendid chap.