Eric Amundson on "Can my 25 websites appear as separate websites? or 1.main.com, 2.main.com...?"

With Multisite, can the websites appear as if they are separate websites, or must they be in the format site1.main.com, site2.main.com / main.com/site1, main.com/site2?
I want viewers to see site1.com, site2.org, etc. Oh, but when they aren't on the homepage, I want the url to display e.g. site1.com/contact or site1.com/category/post, not just always display site1.com for all pages.
Can I do that in Multisite? Does it have server requirements besides the standard server requirements for Multisite?
Thank you!