Good day! (Early morning to me)

First thread here, I hope it's in the right place.
I have a dear friend whom is a fantasy writer(also just GENERALLY seems to love world building)
He has a problem regarding the storing and sorting of all the information he creates, and told me that he'd really love to have something like wikipedia... But private.
So what I'm hoping to find is some sort of database program with a search engine(my father also told me to include that it needs a graphical interface, eh...)
So, um, yeah.
Easy to use, free.
Just create an article, tag to include in a category, easily searchable.
A private wiki program.

Does this exist?


Thank you on beforehand. Yes, there are. But the free ones are not as good.

A database has to be indexed  to be useful.

The subject is much to wide and deep to cover here. It is more that knowing how to program. In fact, you will have more good RESULTS if you just skip over the theory and the programming. LOOK this over:

http://en.wikipedia.org/wiki/Full_text_database

It is helpful  if the full text is in manuscript form. Which MEANS no SPECIAL formatting or fonts. Just tests. Or else choose a tool that will ignore the formatting of a Word document and just index the text.
Never mind. Ignore that.
Just concentrate on the idea of a full text database.
This link has a list of free tools to make your own database.
http://en.wikipedia.org/wiki/Full_text_search
Hope it t helps.