Release format number of version (10.2.0.1.0) in Oracle:

First two digits (10): Version Release Number
The version number, such as 10 or 1, is the most general identifier. A version is a major new edition of the software, which usually contains significant new functionality.

Second digit (2): Maintenance Release Number
The maintenance release number signifies different releases of the general version, starting with 0, as in version 10.0. The maintenance release number increases when bug fixes or new features to existing programs become available.

Third digit (0): Application Release Number
The third digit reflects the release level of the Oracle Application Server (Oracle AS).

Fourth digit (1): Component-Specific /Patch Release Number
The fourth digit identifies a release level specific to a component. The patch release number identifies a specific level of the object code, such as 11.1.0.1. A patch release contains fixes for serious bugs that cannot wait until the next maintenance release. The first distribution of a maintenance release always has a patch number of 0.

Fifth digit (0): Platform Release Number
A platform release number can be used to identify a particular emergency patch release of a software product on that operating system, it usually fixes or works around a particular, critical problem.