Can you please explain the Discuz! Code to me?

Can you please explain the Discuz! Code to me?
You can use BB Code, a simplified version of HTML, in your posts to create certain effects.

  1. [b]Bold Text Abc[/b]   would produce: Bold Text Abc (Bold Text)

  2. [i]Italicized Text Abc[/i]   would produce: Italicized Text Abc (Italicized Text)

  3. [u]Underlined Text Abc[/u]   would produce: Underlined Text Abc (Underlined Text)

  4. [color=red]Text Abc in Color Red[/color]   would produce: Text Abc in Color Red (Change Color of Text)

  5. [size=3]Text Abc in Size 3[/size]   would produce: Text Abc in Size 3 (Change Size of Text)

  6. [font=Tahoma]Text Abc of Tahoma[/font]   would produce: Text Abc of Tahoma (Change Font of Text)

  7. [align=Center]This is centered[/align]   would produce:
    This is centered
    (Centered Text)

  8. [url]http://www.comsenz.com[/url]   would produce: http://www.comsenz.com (Hyperlink)

  9. [url=http://www.Discuz.net]Discuz! Board[/url]   would produce: Discuz! Board (Hyperlink)

  10. [email]myname@mydomain.com[/email]   would produce: myname@mydomain.com (E-Mail Hyperlink)

  11. [email=support@discuz.net]Discuz! Technical Support[/email]   would produce: Discuz! Technical Support (E-Mail Hyperlink)

  12. [quote]Discuz! Board is a bulletin board system developed by Comsenz Inc.[/quote]   (Quoted Text, similar code [code][/code] for quote program codes)

  13. [hide]Hidden Text[/hide]   (Hide Text to Visitors Unless Replying this Thread)

  14. [hide=20]Hidden Text[/hide]   (Hidden Text According Visitor's Credits

  15. [list]
    [*]first bulleted item
    [*]second bulleted item
    [*]third bulleted item
    [/list]   (Lists)

  16. [fly]This is sample text[/fly]   (Scroll the content horizontally, just like "<marquee>" in HTML, Attention! Only effective in IE)

  17. Flash Movie   (Insert Flash)

  18. [ra]rtsp://your.com/example.ra[/ra]   (Insert Real Audio)

  19. [rm]rtsp://your.com/example.rm[/rm]   (Insert Real Audio/Video)


    20. Below codes are available only when [img] code is allowed

  20. [img]http://top.igg.com/forum/images/default/logo.gif[/img]   (Image)
    would produce:


  21. [img=88,31]http://top.igg.com/forum/images/logo.gif[/img]  (Resized Image)
    would produce:


  22. [swf]http://top.igg.com/forum/images/banner.swf[/swf]   (Shockwave-flash)