Apple released OS X 10.9 Mavericks developer preview 4 on Monday. We haven't yet seen patch notes for the release, but the company has used the developer previews to roll out steady improvements and updates to new features.
In other words, we don't yet know what's specific to this release.
Apple has been on a two-week release cycle since the company announced Mavericks at June's World Wide Developer Conference. It was unclear if Apple would keep to that schedule this week after the company confessed over the weekend that its developer site was hacked last week, but here we are.
Apple shut down that developer site while it reworks security, and that's why we haven't seen patch notes.
Since we don't know what's new in this release, we'll use the opportunity to show our concept for the Mavericks logo. I posted it to Instagram a few weeks ago, but this seemed like as good a time as any to publish it on TMO.
If it doesn't make any sense, ask your parents. Or maybe your grandparents.