pip is a replacement for easy_install (from pysetuptools).  It uses mostly
the same techniques for finding packages, so packages that were made
easy_installable should be pip-installable as well.

pip is meant to improve on easy_install.  Some of the improvements:

- All packages are downloaded before installation.  Partially-completed
  installation doesn't occur as a result.
- Care is taken to present useful output on the console.
- The reasons for actions are kept track of.  For instance, if a package is
  being installed, pip keeps track of why that package was required.
- Error messages should be useful.
- The code is relatively concise and cohesive, making it easier to use
  programmatically.
- Packages don't have to be installed as egg archives, they can be
  installed flat (while keeping the egg metadata).
- Native support for other version control systems (Git, Mercurial and
  Bazaar).
- Uninstallation of packages.
- Simple to define fixed sets of requirements and reliably reproduce a set
  of packages.

pip is complementary with virtualenv, and it is encouraged that you use
virtualenv to isolate your installation.