I need a little clarification on website URLs

I need a little clarification on website URLs. If a search is done to find my website, let’s say www.mysite.com, when they find mysite, are they view it as, www.mysite.com/Default.aspx? Is it possible then for me to replace “Default.aspx” with words that relate more to my site? For example: www.mysite.com/makeup.aspx so that the page content, meta data and URL relating to makeup will be cached by google.
Please confirm if this is possible. Thanks.
