This inserts an image into your document. You should provide a URL to the image between the start and end [img] tags, like this:
Google's logo: [img]http://www.google.com/intl/en_ALL/images/logo.gif[/img]
--> Google's logo:
Alternatively, if you instead use a partial filename (which must start with an alphanumeric character or an underscore), the [img] tag will locate the file relative to the defined local image directory, and will (A) determine that the image file actually exists on the local server and (B) insert correct width/height for it as well, which can speed page loading. For example, if you run a webcomic site, it may be beneficial to set your local image directory to /comics, so that you can then include individual comics just by writing [img]20080704.jpg[/img]. Any filename which starts with a . or a / will not be considered a local image file.
This inserts a horizontal rule (separator bar) into your document. When you use the shorthand ----- form, NBBC converts it into a [rule] tag. The default behavior of the [rule] tag is to generate a <hr /> HTML element as its output; this behavior can be changed with the SetRuleHTML function. The [rule] tag does not have an end tag.
This inserts a break (<br />) into your document; it is equivalent to a carriage return, but unlike a carriage return, it can't be "eaten" by a nearby block tag like [center]. The [br] tag does not have an end tag.