These files contain the aliases and environmental variables made available to Bash running as a user shell and to all Bash scripts invoked after system initialization.
Systemwide defaults, mostly setting the environment (all Bourne-type shells, not just Bash )
systemwide functions and aliases for Bash
user-specific Bash environmental default settings, found in each user's home directory (the local counterpart to /etc/profile)
user-specific Bash init file, found in each user's home directory (the local counterpart to /etc/bashrc). Only interactive shells and user scripts read this file. See Appendix K for a sample .bashrc file.
user-specific instruction file, found in each user's home directory. Upon exit from a login (Bash) shell, the commands in this file execute.
A listing of all the user accounts on the system, their identities, their home directories, the groups they belong to, and their default shell. Note that the user passwords are not stored in this file,  but in /etc/shadow in encrypted form.
Listing and description of attached hardware devices. This information is in text form and can be extracted and parsed.
bash$ grep -A 5 AUDIO /etc/sysconfig/hwconf class: AUDIO bus: PCI detached: 0 driver: snd-intel8x0 desc: "Intel Corporation 82801CA/CAM AC'97 Audio Controller" vendorId: 8086
This file is present on Red Hat and Fedora Core installations, but may be missing from other distros.
This does not apply to csh, tcsh, and other shells not related to or descended from the classic Bourne shell (sh).
In older versions of UNIX, passwords were stored in /etc/passwd, and that explains the name of the file.