Production vs development version numbers

[Joshua Stewart]

I understand that even numbered versions are considered "stable"
releases and odd numbers represent development versions, but there are
some details I don't yet understand.

If an even version is "stable", what types of differences are there
between different patch levels of an even version, for example 2.4.x and
2.4.y.  Are these bug fixes, performance boosters, or functionality
additions?

Also, when fixes are made to a stable version kernel, such as those
added to 2.4.19 to give us 2.4.20, do those fixes get incorporated into
the current development version as well?

Thanks,
	Josh (a kernel newbie)