Grid

In graphic design, a grid is a structure (usually two-dimensional) made up of a series of intersecting straight (vertical, horizontal, and angular) or curved guide lines used to structure content.

The designer's guide to grid theory
Creative Bloq
The Grid System: Articles
The Grid System
All About Grid Systems
EnvatoTuts+
Fluid Grids
A List Apart
A Brief History of Grids
Graphics
Thinking Outside the Grid
A List Apart