Pacman is a package manager. With Pacman, you can transparently fetch, install and update software packages. The packages can be any mix of tarballs rpm or other types. The advantage of using pacman is that all the annoying details of doing this, such as:
Ideally, if something in this procedure doesn't work, you get to complain to the person who setup the "software cache" rather than fixing it yourself. That way, if a problem comes up, it can get solved once rather than forcing everyone to fix it individually.
To use Pacman, you need a unix system and Pacman will also insist upon Python 1.5.2 or later. Given this, just unzip and untar the pacman-XXX.tar.gz file, cd into the directory containing README and source the file setup.csh or setup.sh depending on your shell. You're now ready to try the tutorials.
A number of people have helped Pacman in one way or another, none more than Alain Roy of the University of Wisconsin. More information about the epic saga of Pacman will come with the next major release, coming soon...
If you're finding Pacman helpful or have questions, comments or problems, or if you just want to say hi, drop me an email at youssef@bu.edu.