Help about display modes (screen resolution):
[First of all, this guide was written in 2004 or so.. These days, even displays on mobile phones have far higher resolution than most computer screens in 2004, Still, could be relevant for someone using ancient or retro computers.]
A required display mode of e.g. 800*600 means that your monitor/screen displays 600 horizontal lines that are each 800 pixels wide. This means that more 'stuff' fits onto the screen compared to a 640*480 display where you only have 480 horizontal - 640 pixels wide- 'pixelrows'.
(The amount of pixels width/height is usually referred to as 'screen resolution.)
e.g. If you have a picture that is 700 pixels wide, it would not fit onto a 640 pixels wide display. What happens is that you get 'scroll-bars' that let you scroll sideways. This is awkward and avoided if possible.
By having a display resolution of at least 800x600, you will avoid seeing sideway scrollbars...
Nowadays, very few desktop computers have a 640x480 resolution limitation so 800x600 should not be a problem for anyone, except users of hand held internet capable computers. These computers tend to have small screens and that is something we'll have to live with for a while.
How to check your current Display Mode:
(Windows95/NT4.0, MacOS, Amiga OS, Linux)
Click on the 'Start' button, choose Settings /ControlPanel, this opens the Control Panel!
Now double-klick on the 'Display' icon. This brings up the 'Display Properties window. Choose 'Settings'. Now you can see the display size (screen area) on the right side under 'Desktop Area' or 'Settings'. You can also see what color mode you use, to the left under 'Colors'.
(This particular screenshot is from Win XP Pro, other Windows versions may vary slightly in appearance)
(The resolution of this desktop is 1920x1440 and the amount of colors is '32bit' which means 'millions' of colors)
Changing the Settings: You can of course change these settings, but If you don't know what you are doing, ask someone who does. (Otherwise you might select a screen mode that exceeds the limits of your monitor.)
You can without any risc change the amount of colors, though. If it only states '256 colors' you should definitely try to increase that number. Usually, the alternatives are 'HighColor' or 'RichColor' 'thousands of colors' (these usually refer to 65.536 colors) then there's also 'TrueColor', 'RealColor', 'millions of colors' or 24/32 bit (these usually refer to 16.777.216 colors)
If you can't choose a desktop size of 800*600 together with 'HighColor' you probably have a very old graphics card. I suggest you buy a new one ,then. (They are NOT expensive)
Click on 'TheApple', choose ControlPanels /Monitors
Now you can see the amount of colors you use. Click on 'Options' to check the screen resolution.
If you intend to change these settings, read the note above 'Changing the settings (Win95)'
Amiga OS & Linux
Amiga & Linux users aren't lamers, they know what a display mode of 800x600 means... :)
In other words I don't have to explain...