Timing-driven placement
Beginner
Putting the parts on the slowest signal paths extra close together, so their signals arrive in time.
Novice
Placement that checks, during the run, which signal paths come closest to missing the clock deadline, and tells the placer to keep the wires on those paths extra short.
Expert
Usually net reweighting: at a few checkpoints the placer runs timing analysis on estimated wire parasitics and multiplies the wirelength weight of low-slack nets. Path-based and Lagrangian formulations also exist. Over-weighting a few nets can create density hot spots and lengthen everything else.