This package is an OO-abstraction to the SQL-Query language, it provides methods such as setWhere, setOrder, setGroup, setJoin, etc. to easily build queries. It also provides an easy to learn interface that interacts nicely with HTML-forms using arrays that contain the column data, that shall be updated/added in a DB. This package bases on an SQL-Builder which lets you easily build SQL-Statements and execute them. It supports all the db engines supported by MDB.
Since it's a 1:1 port of DB_QueryTool, it has the same API, the only difference being the class name (and the constructor name, of course). You can see the online documentation for DB_QueryTool here