Caret 

The caret is the point at which editing operations occur.  The caret is set by clicking down in the workspace or on a sound.    The caret is made up of a line and 2 triangles.  The triangles show you which track the caret is on.

The caret will obey the current Snap Setting.  Thus, if your snap setting is set to snap to measures, clicking in the middle of measure 3 and 4, will cause the caret to move to measure 3.  

New sounds and recordings are added at the caret position.  After adding a new sound, the caret will move to the end of the sound.  The caret is also the point at which selected sounds will be split.

You can move the caret around by clicking the mouse or by using the keyboard