Group one or more objects together so that you do not accidentally move them.
If you wish to select a child in a group then with the vector select (or vector move tool) active you can either double click on a shape or Ctrl+Click on a one. This will then select the shape under your mouse in that group allowing you to move it around.
When a group is locked you ca not select any children in the group.
Ungroup the objects and delete the group.