The dictionary defines a constraint as being a restricted or confined state within prescribed bounds. Autodesk Inventor LT uses constraints to control geometry within sketches.
The idea that geometry within Autodesk Inventor LT behaves differently depending on the constraints that were applied is one that often hinders new users transitioning from a 2D drawing application.
Within Autodesk Inventor LT's 2D sketch environment constraints are inferred between lines, arcs and other geometry while the geometry is being created. Constraints can also be manually applied to alter the relationships between geometry after the sketch geometry exists. These geometric constraints allow the subsequent editing of the sketch with predictable results. For example, dragging the endpoint of a line that is constrained to be perpendicular to another line does not change the perpendicularity.