What does it mean. => in rails

Can anyone know the meaning for the following symbol in rails?

=>

def update
  account = Account.find params[:id]
  permitted = params.require(:account).permit(:name, :otherparam)
  account.update_attributes permitted
  render :json => account
end

for what purpose we need to use the above expression?

I have searched it in google. but no luck.

Thanks in advance