Relation Command

Relation( <List> ): Shows a message box that gives you information about the relation between two or more (up to 4) objects.
Relation( <Object>, <Object> ): Shows a message box that gives you information about the relation between two objects.

This command allows you to find out whether

two lines are perpendicular
two lines are parallel
two (or more) objects are equal
a point lies on a line or conic
a line is tangent or a passing line to a conic
three points are collinear
three lines are concurrent (or parallel)
four points are concyclic (or collinear).

Some of these checks can also be performed symbolically. If GeoGebra supports symbolic check for a certain property, the "More" button appears. By clicking it, GeoGebra may provide more information whether the property is true in general (eventually under certain conditions).