hi,
in detail, that means after synthesis and p&r, if ur designs seems some tiny timing violation. u can use ipo in your synthesis tool and it will do jobs as follows: buffer insertion, cell resize , etc. but dont change your existing logic.
hi
IPO stands for in place optimisation. This is actually done after floorplan. And actually done during the placement. IPO is done to increase the chances of meeting ur design timing reqiurements which include buffer insertion and resizing of cells and moving the cell instances.