About Branching :

The branching phase of the release cycle lasts around 1 month.
Branching is the duplication of an object under revision control (such as a source code file, or a directory tree) so that modifications can happen in parallel along both branches.
Branches are also known as trees, streams or codelines.
In their main branch NetBSD has 4.99.1 , 5.99.1 and 6.99.1, the branches of 5.99.1 spread to:
-	5 - has a lot ot bug fixes and is stable
-	5.1 - has and many bug fixes
-	5.0 - has the most crucial security branch and lots of bug fixes
The same goes for 6.99.1.

This is how the current NetBSD branching works as of 4.99.1 :
http://www.netbsd.org/images/graphs/release-graph.gif
This is how the branching of NetBSD as of 1.5 to 2.0 :
http://www.netbsd.org/images/graphs/old-release-branches.gif

The most significant change in their branching is the interface and how its more easy for the user to see the changes
that occured over the maintanence branch.


About Formal Releases :

An official release is, believed to be reliable, source and binary distribution of NetBSD can either be in the form of a major release like 5.0 or 6.0, of a maintenance (stable) release such as 5.1, or a security/critical release like 5.1.2.
For each major release there is a corresponding maintenance branch, and after the release of the major release, bug fixes and features with limited scope are ported back to the maintenance (stable) branch.
This maintenance branch will after a while give rise to formal minor releases, e.g. 6.1. A minor release is generally more reliable than -current of the same date, but is missing features compared to -current.
NetBSD has with the release of NetBSD 2.0 introduced the concept of security/critical releases.
These (5.0 , 6.0) are created from CVS branches which are branched off the release points for major and minor releases.
These (5.0 , 6.0) particular maintenance branches only receive bug fixes which either fix security problems or other critical problems.
This is illustrated in a graph showing the release branches.
-	http://www.netbsd.org/images/graphs/release-graph.gif

About Naming Releases in NetBSD :

The version number is always in the form of N.99.M, and will develop into the next formal major release. E.g. 66.99.23 will eventually become 7.0_BETA (and later, 7.0) e.g. 6.0_STABLE, which will evolve into 6.1.

About Binary Compatability :

This is when an already compilated program could be run on a different computer with possibly different CPU architecture.
When you upgrade an operating system, you should assume that some of your existing software that doesn't get upgraded continues to work.
In computing, a computer that can run the same binary code intended to be run on another computer is said to be binary-compatible. This differs from source code compatibility, where recompilation may be necessary.
It means that computer programs that are to be run on multiple operating systems, such as FreeBSD or NetBSD, offer binary compatibility with more popular operating systems, such as Linux-derived ones, since most binary executables are not commonly distributed for such operating systems.
The same applies to Microsoft Windows; most binaries that are compiled for Windows 2000 can also be run on Windows XP and Windows Vista.

About NetBSD Release Information:

You can find more specific information about their major and minor releases on their official website - http://www.netbsd.org/changes/