- Grid line: the horizontal and vertical dividing lines of the grid.
- Grid cell: the smallest unit of a grid, bordered by four adjacent grid lines with no grid lines running through it.
- Grid area: a rectangular area made up of one or more adjacent grid cells.
- Grid track: the space between to adjacent grid lines (generic for grid column, and grid row).
Source: https://webkit.org/blog/7434/css-grid-layout-a-new-layout-module-for-the-web/