The game is played and the stories created on a battlefield. This can be any size, but in practice most will find that somewhere between 4' x 4' and 6' x 4' is the best.
The battlefield is gridded into 24 squares, which for a 6' x 4' battlefield will mean the squares will be around 1' x 1'. The squares need not be the exact size.
The gridding can be done by using a marker pen (not recommended) or by using terrain to mark out the corners of each square.
A battlefield 'gridded' by use of individual trees and clump foliage
Another example of how to incongruously grid your battlefield
This example of gridding uses a large clump of rocks (left, top centre) to grid the battlefield along with individual trees and the ubiquitous pieces of clump foliage
The advantages of gridded battlefields? Manifold.
Speed of play. - removing measuring for movement and firing etc. increases speed of play by almost 100%.
Accuracy - figures are clearly within range or without range, an extra few mm here or there is NOT of critical importance.
Aesthetics - no more balancing figures on a hill to show EXACTLY where they are, no more hesitation about putting on the battlefield a wood or marsh because of the mental arithmetic such a terrain items cause, battle lines that are not too regular or irregular etc.