Thats a pretty decent definition. I think their phrase "incompatible type systems" is meant for you to stress the word systems. The word type is not needed. Not to be confused with "type of an object, i.e. its class".
If you really want to know what's in various lower level drivers, as opposed to ORM frameworks (which vary quite a bit themselves), just go crack open some code and look at the APIs for yourself. You can go pretty far back to MS ODBC libs or even vendor dependent Oracle libs from mid to late 80s and see they were used quite effectively on their own for many years. JDBC was fairly straightforward derived from these predecessors.
