i have Ubuntu 14.04.3 LTS installed i heard that lts versions are supported for 5 years but why only 14.04.1 is supported for 5 years and not 14.04.3 ? even though 14.04.3 is LTS ? im confused why do they name it LTS then .
14.04.3 is not a "real" release. It is similar to Windows Service Packs. You do not say that Windows 7 SP2 is a release. Even when you can get an installation media with a SP included.
"Point releases" just accumulate security updates and bug fixes. And also add optional HWE Stack support.
The main release is 14.04. It is supported for 5 years since April 2014.