I am attempting to point a website title to some single page, and the domain exactly the same (no redirect).

Therefore if a person types: world wide web.domain1.com.au --> original website is proven

If your user types: world wide web.domain2.com.au --> they're proven world wide web.domain1.com.au/second.php, however the URL still states world wide web.domain2.com.au.

Is this done using .htaccess?

Snippet of current .htaccess file is:

RewriteCond % www.domain2.com.au [NC]

RewriteRule (.*) /two [L]

RewriteCond $1 ^(onetwothreefour) [NC]

RewriteRule ^(.*)$ /index.php/$1 [L]

So essentially the world wide web.domain2.com.au must display the world wide web.domain1.com.au/two page, which is really world wide web.domain1.com.au/index.php/two

You can certainly make a move such as this:

RewriteCond % ^(www.)?domain1.com.au$

RewriteCond % !^/domain1

RewriteRule (.*) /domain1/$1 [L]

RewriteCond % ^(www.)?domain2.com.au$

RewriteCond % !^/domain2

RewriteRule (.*) /domain2/$1 [L]

Your exact situation would such as this:

RewriteCond % ^(www.)?domain2.com.au$

RewriteRule (.*) /second.php [L]

Edit: Since you have published a snippet do this rather:

RewriteCond % www.domain2.com.au [NC]

RewriteRule (.*) /index.php/two [L]

RewriteCond $1 ^(onetwothreefour) [NC]

RewriteRule ^(.*)$ /index.php/$1 [L]

You need to show another site than the URL states.

That needs proxying.

Look at this: http://httpd.apache.org/paperwork/2./mod/mod%5Fproxy.html