1. History of computers
What your computer can do depends upon two things: the hardware your computer has, and the software that can be run on your computer.  Hardware are physical components that make up your computer.  Any part of your computer that you can see or touch is hardware.  Software are programs or applications that run on your computer.  Without software, the hardware would be useless because the software tells the hardware what do to.
For example, most computers can view web pages.  Computers need both hardware and software to do this.  Hardware it needs includes a modem or Ethernet card, processor and monitor.  Yet, hardware alone can not show you web pages.  Although you have the modem or Ethernet card to connect to the Internet, and the monitor to display the web pages for you, without the software your computer can not make the modem work, find the right web page on the web, or figure out how to bring it to your computer and display it properly.  You can think of software as part of the "brains" of your computer.

2. Essential Computer Components
Motherboard
Essential Computer Components
The Case This Case is the "box" or "chassis" that holds and encloses the many parts of your computer.  Its purpose is to protect them from damage and dust.  The case is usually made of metal.
The Motherboard If you open your computer's case, you will see various wires, chips, slots, etc.  The largest circuit board is called the Motherboard.  It holds and connects all the important parts of your computer together.
Internal Hard Drive When you think of a Hard Drive, think of Long Term Memory.  The hard drive stores your operating system, software programs, and many other files.  Hard drives in personal computers are non-removable.
The Processor (Microprocessor or CPU-Central Processing Unit) Attached to the motherboard, the main processor acts as the brains of your computer.  It processes all the instructions given to your computer. 
RAM (Random Access Memory) When you think of a RAM, think of Short Term Memory. Before you computer can open software, it must first copy it temporarily to your RAM. 
Expansion Slots and Cards When you want to add something to your computer, your first step is to see if you have any unused Expansion Slots.  Expansion Slots are ports in your motherboard to which you can additional hardware. 

3. Computer Connections
1 -Power Adapter In This is where the power cord connects to the computer.
2 - DVI Video Output This is a digital video connection that sends the signal to your monitor.  It replaced the older analog VGA connection.
3 - Serial Port This has been a popular port for many years because of its versatility.  It has been used to connect the computer to just about every peripheral device on the market. 
4 - USB 2.0 Ports The Universal Serial Bus allows you to "daisy chain" several USB devices together, then connect them to your computer through just one connection.
5 -Parallel Printer Port Commonly referred to as the "Printer Port", the Parallel Port will transfer data faster than the serial port. 
6-Ethernet/Network Jack This is what high speed modems (DSL & Cable) use when then connect to your computer. 
7-Line In Port This is where you plug your computer's microphone in to record your voice.
8-Speaker Out Port Your computer's speakers and/or headphones plug into this port.

4. Computer Input Peripherals
The Traditional Flat-Bed Scanner
Computer Input Peripherals
Mouse The mouse is simply a device used for pointing, selecting, and highlighting things visible on your monitor.  Traditionally, most mice have used a mouse-ball on its underside to navigate around the screen as you move the mouse. 
Keyboards As with the mouse, people have experimented with how to make the keyboard more user-friendly. 
Scanners You can think of the scanner as the "eyes" of your computer.  Scanners allow you to convert anything it can scan to a digital image, which it then stores inside your computer.
Digital Cameras The biggest difference between digital cameras and traditional cameras is that digital cameras do not use film.
Graphics Tablets This is a great tool for those web designers and graphic artists who rely upon free-hand drawing to make graphics. 

5. Computer Output Devices
Speakers Many people today use their personal computer to listen to music.  You can now purchase speakers for your computer similar in quality to those you would find with a stereo system. "Higher-end" speakers often feature volume control, a sub-woofer for a deeper sound, and upon occasion, rear speakers for "Surround Sound."
Printers The two most common printers today are the Photo and All-In-One printers. Photo printers print on photo paper of various sizes.  All-In-Ones print with very good quality and are versatile with the ability to print labels, envelopes, and more.  All-In-Ones can offer phone, fax, scanner and copier. These printers are very popular because save space, where before you had to make room for all these different machines in your work area, now you just have one device. 

6. Drives and Media
CD/DVD Drive Computers typically play both DVDs and CDs in the same drive.  DVD can hold approximately 5GB of information.  They first broke into the market as a format from which to watch movies.  They have begun to push CDs out of the market.
USB Drive (Also called Jump, Flash, or Thumb Drive) The newest drive to gain popularity is the USB Drive or Flash Drive.  This is also known as the "thumb" drive since it is about the size of your thumb. 
External Hard Drive When it comes to file and media storage, the best "bang for your buck" definitely belongs to the external hard drive or disk.