Row and site
Beginner
The neat lanes on a chip where the small parts must sit, split into equal slots like spaces in a parking lot.
Novice
The core of the chip is tiled with horizontal rows, each exactly one cell tall. Each row is divided into equal slots called sites, the smallest step a cell can be placed at. A cell must start on a site boundary, and its width is a whole number of sites. Every other row is flipped so neighboring rows can share the power or ground wire along their common edge.
Expert
The site comes from a LEF SITE statement (size, symmetry); DEF ROW statements lay rows out with an origin, an orientation and a site count and step. Multi-height cells span several rows and must match the power/ground rail pattern, which limits which rows and orientations are legal for them.