Designs are hierarchical. That means, that in the main design (also called top cell) has references to other cells (cells are also called instances or blocks). In this way repeating structures need only be created and stored once, design will get smaller and easier to maintain. However editing may get a little bit more difficult as alway the correct cell to be edited has to be opened.
With the Edit-inPlace feature it is possible to edit not only the current cell but also any referred cell without changing the existing view and make editing of hierarchical design more simple. With Cell Descent (in the context menu of the edit/select mode) or the the cell/edit-in-place/select feature you can switch to the referred cell without changing the view. With changing the edited cell all the other cells will be shaded light gray and it is easy to see which cell is being edited. Going up again to the mail cell is possible similar with a cell up (in the context menu or in cell/edit-in-place/cell up).
A cell may be referred more than once in a design with the feature Move Cell Left, Move Cell Right, ... You can navitage through all appearances of the referred cell and edit it at that location. Edit-in-Place wiith work hierarchical. You can switch from the main cell down to the deepest referred cell in the design. There is no limitation in hierarchie levels. Some feature that change the global cell hierarchie will end any Edit-in-Place and switch back to the main cell.