Specifies that this version is for Intel-based Mac computers, as Mavericks was released well after Apple's transition away from PowerPC processors.
This likely refers to the installation method, indicating it was downloaded and installed via the Mac App Store. Mavericks — 10.9.3 (App Store) [Intel]
This is OS X 10.9, released by Apple in 2013 [1]. Specifies that this version is for Intel-based Mac