YY: Year (14 = 2014)
MM: Month (04 = April, 10 = October)
K: Kernel Update (every few months an LTS version will get a point update, like your iPhone may be on iOS 8.3 right now - not a mjaor upgrade but updates pushed down to LTS from a non-LTS)
What is LTS?
Every two years Ubuntu release an LTS version. These are typically supported for 5 years and will receive updates from newer distros once they are stable. In most cases you should go LTS for stability.
What is Non-LTS?
Every 6 months Ubuntu release a Non-LTS versions, These typically receive updates for 1.5 years or less. These will be less stable than LTS and should not be used if not required or wanted.
What versions are LTS?
LTS versions are every two years.
So for these are the LTS versions:
This should continue in this naming scheme.