Choosing a kernel
The next step is to choose the kernel for your project, balancing the desire to always use the latest version of software against the need for vendor-specific additions and an interest in the long-term support of the code base.
Kernel development cycle
Linux is developed at a fast pace, with a new version being released every 8 to 12 weeks. The way that the version numbers are constructed has changed a bit in recent years. Before July 2011, there was a three-number version scheme with version numbers that looked like 2.6.39. The middle number indicated whether it was a developer or stable release; odd numbers (2.1.x, 2.3.x, 2.5.x) were for developers and even numbers were for end users.
From version 2.6 onward, the idea of a long-lived development branch (the odd numbers) was dropped, as it slowed down the rate at which new features were made available to the users. The change in numbering from 2.6.39 to 3.0 in July 2011 was purely because Linus felt that...
