OverviewWithin most Astro tools is a property referred to as Orb. The Orb controls the amount of variation allowed for a result to be considered as passing / being true.
For example, if a Planetary Aspect for Mars and Venus was set to Square, without an orb value the indicator would only display when the angle is exactly 90 degrees.
Planetary Aspect - Mars / Venus - Square - No Orb
The orb value (2 by default) allows us to add a buffer either side of the 90 value, so that any value between 88 and 92 will display the aspect.
Planetary Aspect - Mars / Venus - Square - With an Orb Value of 2
Some tools will show a shaded zone for the orb, and a vertical line to indicate the date of the exact match.
Update: With the release of the Optuma 64bit v1.3 update the Orb properties for Astro tools have been split into an Orb for Longitude and an Orb for Latitude.
This allows tools to combine Aspects which use Longitude and Latitude in a single tool, rather than having to keep them separate (as Latitude orbs are usually require a much smaller value).