# Thinking in Grid Notation

When beginning to learn about Grid Notation, it may be helpful to think of something like the playhead in a video player. As the video progresses, the playhead moves from left to right. You can fast forward, rewind, and jump around, but the playhead always indicates what “now” means.

Grid notation works similarly. When GuideGuide begins parsing grid notation, the hypothetical “playhead” starts at the left or top of the context, that is, at the coordinate `0`

of the given axis. As grid notation’s commands are processed from left to right, each command is applied from the current location of the “playhead”.

Some commands provide literal movement instructions (`10px`

or `-1in`

), others provide instructions for how GuideGuide should move the “playhead” based on other calculated factors within the grid. Guide commands `|`

tells GuideGuide to add a guide at the current location of the “playhead”.

The following reference explains the different GuideGuide commands and what they do.