Homebrew installs the stuff you need that Apple didn’t put it into their own directory and then symlinks their files into /usr/local.

Here is a simple how-to install brew on Yosemite:

• Download and install Xcode 6.1
• Open your Terminal
• Download the latest Java SE JDK from Oracle
• Run the following commands:

  ruby -e "$(curl -fsSL httpss://raw.githubusercontent.com/Homebrew/install/master/install)"
  
  brew doctor 
  

At this point, brew is installed and ready to use. To install some of the tools/packages it has available, a command “brew install” will be needed.
For example:

brew install nmap

Enjoy your new little bit of freedom.