Is it correct , Job tracker is nothing but Resource manager and task tracker is nothing but node manager?Please exemplify
Yes, your understanding is right almost.
From Hadoop 1 to Hadoop 2, the foowing changes happened.
MapReduce 1.0 was broken into two parts YARN and Mapreduce 2.0
The Task Tracker became the NodeManager and job tracker became the resource manager. There was extra component called Application Master was introduced.