The Grid

A grid is intended to break space or time into regular units. Often, these units are separated by spaces called gutters. The spaces surrounded by the gutters are referred to as modules; this kind of grid is called a modular grid. When applied to typography, this grid is used to make type selection simpler and more useful.

The modular grid is made up of five elements: the module, gutter, margin, column, and flowline/hangline.
The module is the rectangular area that is defined by the negative area between gutters.
The gutter as mentioned in the previous description of a grid is the space which falls between the modules and separates the modules from the edge of the layout.
Margins are the areas that lie at the top and bottom of the pace, ending with the first and last modules.
A column is an area that occupies the width of one module and ranges from margin to margin (top to bottom).
Flowlines and Hanglines refer to the lines of the modules; the flowline referring to those that are horizontal and the hangline referring to those that are vertical.