Today's release of Mac OS X Lion doesn't increment the 10.7.2 version number developers have been using, but does bump the build number from 11C26 to 11C37. In Apple's build system, the first number relates to the reference release of Mac OS X (11 means Lion), while the letter refers to the minor release (C = x.2), while the final number refers to builds within that release.
Apple creates a series of internal builds that are never released publicly, explaining the jump from 26 to 37 in its developer releases. The new incremental advancement is centered around iCloud, which has become the company's focus under both Mac OS X and iOS 5.
Apple has been packaging iCloud functionality as a separate installer for Lion, which itself only lays the groundwork for iCloud services. Along with the new build of Lion comes a new revision of this "iCloud for OS X Lion" package, which must be installed on top of the new Lion build.
Earlier this week, Apple issued an update to the developer build of Safari 5.1, which is identified as 5.1.1. It too is focused on resolving any issues with iCloud sync of Bookmarks and Reading List items.
A separate iPhoto 9.2 beta 2 has also been released this month to scout out any potential issues with iCloud's Photo Stream, which automatically pushes new photos captured by mobile devices or imported from cameras to machines registered with iCloud into a pool that is then kept up to date with iPhone, iPod touch, iPad and Mac photo libraries, or copied to the photos directory of a PC.