cPanel is a fully featured web-based control panel that allows you to manage your domain through a web interface. The idea is to transfer as much of the control and responsibility of managing your web site to you. You have the ability to manage all aspects of e-mail, files, backup, FTP, CGI scripts, and web site statistics.

The control panel built by cPanel offers two levels of web server administration, Webhost Manager (WHM) and cPanel. WHM allows web based management abilities that include administering individual and reseller accounts and perform basic system maintenance.

WHM features includes:

Basic Skinable User Interface
Ability to Change Automatic Update Schedule
Change Hostname
Set Server Time
Three Different Reseller Systems
Unix Quota Support
Ability to Change MySQL Root Password
Disable/Enable Suexec
Wheel su Security
Remote Access Keys
Interactive Knowledge Base
Server Backup and Restore
Config File Rollback
Graceful and Forceful Reboot Support
Service Status Page
Server Info Page
Quick Access to Apache Status
CPU/Memory/MySQL usage history
Ability to limit users disk space, bandwidth, POP accounts, FTP accounts, shell access, SQL databases, lists and subdomains
Account Upgrades/Downgrades
Ability to rearrange accounts (move access between disks)
Suspension of Accounts
Email all users
Change users' passwords
Change ownership of an account (move account between resellers)
Demo Mode
Custom Suspension Pages
Ability to Copy Accounts from other servers, including: cPanel, WebPanel, Plesk, CiHost/Spectro, Ensim, Alabanza
Built in cPanel/WHM Theme Manager
Access to Addon cPanel Themes
Domain Parking/Pointing
Add a DNS Zone
DNS Zone Editor with syntax checker
Ability to Host DNS on a remote machine
Domain Forwarding
Install FrontPage Extensions
Reset the MySQL Root Password
Repair a Database
Change a Database user's password
Manage IP Addresses (Add/Remove)
Format new Hard Disks
Optimize EIDE hard drives
Install Perl Modules
Mail Troubleshooter
Manage Mail Queue
View Mail Stats
Background Process killer (detect & kill IRC bots)
View System Processes
Reset a Mailman (Mailing List) Password
Update to the latest version with a Click
Change the SSL Certificate cPanel/WHM uses
Generate a new SSL Certificate
Install an SSL Certificate
Restart Services

cPanel is the other layer of the control panel administration that allows end user to control everything from adding / removing email accounts to administering MySQL databases. The comprehensive list of cPanel's ability can be found below.

Backup & Restore
Manage Email Accounts (Add, Remove, Change Password)
WebMail for all Accounts
Auto Responders
Custom Mail Filtering
Forwaders
Mailing Lists (mailman)
Ability to Modify an MX Entry
Spam Filtering
Webalizer Web Stats
Webalizer Ftp Stats
Analog Stats
AWStats
View Latest Visitors
View Bandwidth Usage
View Error Log
Download a raw log file
Manage FTP Accounts (Add, Remove, Change Password)
Anonymous FTP Controls
Ability to change FTP login message
Ability to kill FTP sessions
Site Tools
Web Protect (htaccess editor)
Ability to Change Site and FrontPage password
Custom Error Pages
Redirects
Ability to Edit Mime Types
Ability to Edit Apache Handlers
Install FrontPage Extensions
Uninstall FrontPage Extensions
Search Engine Submit Tool
File Manager
Ability to Add/Remove Subdomains
Subdomain Redirects
Stats for Subdomains
SSH access
Manage GPG Keys
Cron Jobs
Pre-Installed CGI Scripts
Interchange Cart
Agora Cart
Bulletin Board
Java Chat
HTML Chat
phpMyChat
CGI Wrapper (for non-suexec installs)
Random HTML Generator
Advanced Guestbook
Counter Generator
Java Clock Generator
Java Countdown Generator
Secure FormMail clone
cgiemail
Entropy Search
Entropy Banner
DNS Lookup
Traceroute
Database Management
Manage MySQL Databases (Add, Remove, Change Password, Add Access Hosts)
phpMyAdmin Access

Demo WHT here.

LOGIN NAME: root
PASSWORD: whmdemo

Demo cPanel here.

LOGIN NAME: cpdemo
PASSWORD: cpdemo

Want to learn how to optimize cPanel control panel features? Download cPanel manuals here.