Wikipedia uses alphabetical ordering for page names in categories to make it easier to find what you are looking for. The special page which lists all pages on Wikipedia also uses alphabetical ordering.
The alphabetical order used by Wikipedia is based on the Unicode order and corresponds to American Standard Code for Information Interchange.
Blank spaces between words in a page name are treated as an underscore "_", and are therefore ordered after upper case letters and before lower case letters. Blank spaces after a page name come before any character.