From the Introduction:

PHP is a wonderful language for building dynamic web pages.
Unfortunately, PHP's database access functions are not standardised.
Every database extension uses a different and incompatibile API.
This creates a need for a database class library to hide the differences
between the different databases (encapsulate the differences) so we can
easily switch databases. 

ADODB stands for Active Data Objects Data Base.

ADODB currently supports:
	MySQL, PostgreSQL, Interbase, Oracle, MS SQL 7
	Foxpro, Access, ADO, Sybase, DB2 and generic ODBC.

WWW: http://php.weblogs.com/adodb/