To create a link with control over what text is actually displayed - use the [url=] [/url] construct.
For example:
if you wanted to link to
http://www.somewhere.com/somepage.html and have people viewing the page see the words "Some Link" rather then the address of the site the bbText code would be:
[url=http://www.somewhere.com/somepage.html]Some Link[/url]
Note: the http:// part must be included.
If the link is a page on this web site you can skip the http:// and the address of this web site out and have just:
[url=/somepage.html]Some Link[/url]