Kline: I assume you mean differences between the logical and physical models. The logical model explains the database design without going all the way down to the level detail used to specify its physical format or database platform specifics. As such, many logical models might be a full Entity-Relationship Diagram (ERD) but only have generalized data types along with attributes like NULL/NOT NULL and check constraints. The physical model is likely to go all the way to code, using platform-specific syntax, such that a physical model for Oracle would not be able to run on a SQL Server instance and vice versa.
The physical model will also, of course, have all the details about where the database sits on the file system, the number-location-size of database files and log files, and other characteristics of databases that are specific to the given instance on which you are deploying. Another example might be how each data platform implements a monotonically increasing primary key, for example using an IDENTITY on SQL Server but using a SEQUENCE on Oracle.