Just need a pointer.

I am completely new to recording. I have been going through the tutorials as time permits. Anyway , whenever I am recording on the second “sample ?” it stops where that grey highlight ends. What is it and how do I remove it ? I tried to undo it but it didn’t work. Also on another recording I clicked on the bar to listen to a specific part now whenever I record or play it starts form there ? Thanks in advance people.

The grey bar indicates the “selection” region.
If you don’ want to limit the second track to that duration, press the rewind button (or the “Home” key) before you start recording the next track.

Recording starts from the position of the “playback cursor”. Pressing the rewind button will place the playback cursor at time=0.0. Clicking on a track will set the playback (and recording) position to wherever you click.

More about selecting audio here: http://manual.audacityteam.org/o/man/audacity_selection.html