How to perform the actions "Lift and Insert Selection" and "Lift and Owerwrite" Selection "

Lift or Exract remove the selection from the Sequence.  Lift leaves a Gap while keeping the Sequence duration the same and Extract leaves no Gap (that is, it close the Gap what would have been left had you done a Lift) while shortening the duration of the Sequence.  The selection in this context is whatever footage in the Sequence is between the In Mark and/or Out Mark.  An easy way to review this in an obvious way is to drop a long clip into a Sequence.  Mark an In somewhere after the Sequence start.  Then Mark an Out somewhere a little bit later.  Then do a Lift.  There will be a Gap where the In Mark and Out Mark was..

Insert or Overwrite add the selection to the Sequence.  Insert makes room for the selection being added, pusshing existing clips to the right (adding an edit if necessary) and the durartion of the Seqeuence gets longer..  Overwrite replaces exsiting clips and the duration of the Sequence remains the same.  The selection in this context is whatever video and/or sound is between the In Mark and/or Out Mark in the Source tab.  If the Sequence is empty, Insert and Overwrite can appear to be the same.  And easy way to review this is to place a long clip in the Sequence (let's say, 1 minute), place the Playhead at ten seconds (0:00:10:00), and then Insert a short clip (15 seconds or so).  Undo and then repeat with an Overwrite.  

Most importantly, remember that Insert, Overwrite, Lift, and Extract each obay the Track Targeting.

Hit F1 and type in "Lift and Insert Selection" or "Lift and Overwrite" Selection.

Some Tutorials to help you get started
https://helpx.adobe.com/premiere-pro/get-started.html
https://community.adobe.com/t5/premiere-pro/premiere-pro-tutorial/td-p/10974406?page=1
https://community.adobe.com/t5/video-lounge/tips-amp-tricks-to-become-a-premiere-pro-power-user-with-abba-shapiro/td-p/10900149?page=1
https://community.adobe.com/t5/video-lounge/video-series-real-premiere-pro-secrets-by-cut-to-the-point/td-p/10900176?page=1
https://community.adobe.com/t5/video-lounge/podcast-art-of-the-cut-coup-53-editor-walter-murch-ace/td-p/10887889?page=1
https://helpx.adobe.com/premiere-pro/how-to/premiere-pro-nesting-sequence-cc.html