pip defaults to installing Python packages to a system directory (such as `/usr/local/lib/python3.4`). This requires root access.
`--user` makes pip install packages in your home directory instead, which doesn't require any special privileges. ## Other details
The `--user` option is not a valid for every command. For example `pip uninstall` will find and uninstall packages wherever they were installed (in the user folder, virtual environment folder, etc.) and the `--user` option is not valid.
Things installed with `pip install --user` will be installed in a local location that will only be seen by the current user account, and will not require root access (on *nix) or administrator access (on Windows).
The `--user` option modifies **all** `pip` commands that accept it to see/operate on the user install folder, so if you use `pip list -- user` it will **only** show you packages installed with `pip install --user`.

pip defaults to installing Python packages to a system directory (such as `/usr/local/lib/python3.4`). This requires root access.
`--user` makes pip install packages in your home directory instead, which doesn't require any special privileges.