Physical design flow.

Physical design flow or otherwise called as P & R flow.
Back end flow:

1.Floorplanning
2.Placement
3.Clock tree Synthesis
4.Routing
5.Parasitic Extraction
6.Backannotation to STA
7.Physical verification
8.Tapeout

What is a IC layout,mask design or IC mask layout?

Layout is the representation of an integrated circuit in terms of polygons ,geometric shapes which represent metal, oxide ,semiconductor layers that make up the component.
Layout is the top view of the component containing polygons of definite shape and size which represents semiconductor layers,metal,poly,Field oxide that make up the component.