What's the difference between varchar, varchar2?

Монгол хэл дээр бичигдсэнийг харахыг хүсвэл:
http://mongolcoder.blogspot.com/2008/03/varchar-varchar2.html

Varchar and varchar2 are data types of Oracle DB and what's the difference between them?
First: Size, varchar can store 2000 bytes information, but varchar2 can store 4000 bytes information.
Second: Encoding or language chooser(:D), varchar supports ascii, but varchar2 supports unicode.
In addition to this, mongolian character's take 2 bytes space, but english characters take 1 bytes space.