before vs before each vs before all

gistfile1.txt

require 'spec_helper'
 
$count = 0
$count_each = 0
$count_all = 0
 
shared_examples_for "before :each" do 
  it { should == 1 }
  it { should == 2 }
end
 
describe "before" do 
  before do 
    $count += 1
  end
 
  subject { $count }
  it_should_behave_like "before :each"
end
 
describe "before :each" do
  before :each do 
    $count_each += 1
  end
 
  subject { $count_each }
  it_should_behave_like "before :each"
end
 
describe "before :all" do 
  before :all do 
    $count_all += 1
  end
 
  subject { $count_all }
  it { should == 1 }
  it { should == 1 }
end