There are many types of constraints in NX that allow the user to fully constrain their model. Below is a list of notes on NX constraints. All can be found by clicking 
Assembly Constraints.
•Touch Align
Orientation lets you influence possible solutions for a Touch Align constraint as follows:
•Prefer Touch — Presents a touch constraint when touch and align solutions are both possible. (Touch constraints are more common than align constraints in most models.)
Prefer Touch presents an align constraint when a touch constraint would over-constrain the assembly.
•Touch — Constrains objects so their surface normals are in opposite directions.
•Align — Constrains objects so their surface normals are in the same direction.
•Infer Center/Axis — Specifies that when you select a cylindrical, conical, or spherical face, or a circular edge, NX uses the object's center or axis itself for the constraint.
•Angle
Subtype specifies whether the angle constraint is:
•3D Angle — Measured between two objects without requiring a defined axis of rotation.
•Note: The value of a 3D angle constraint is 180 degrees or less. Because a 3D angle constraint defines the angle in space between two objects without using a defined axis, the minimum angle between objects is to solve the constraint.
•Orient Angle — Measures the angle constraint between two objects, using a selected axis of rotation. It can support up to 360 degrees of rotation.
•Center
Subtype specifies whether the center constraint is:
•1 to 2 — Centers one object between a pair of objects.
•2 to 1 — Centers a pair of objects along another object.
•2 to 2 — Centers two objects between a pair of objects.
Axial Geometry appears only when Type is Center and Subtype is 1 to 2 or 2 to 1.
Specifies what NX uses for the center constraint when you select a face (cylindrical, conical, or spherical), or a circular edge:
•Use Geometry — Uses the face (cylindrical, conical, or spherical) or edge for the constraint.
•Infer Center/Axis — Uses the center or axis of the object.
•Bond
Constrains selected objects together so they must move as a rigid body.
•Distance
Displays the distance value between the selected objects and lets you specify the behavior of the distance when the components are moved..
If you want the distance value you specify to:
•Remain constant - Select the Distance 
check box to define the constraint as driving. Other constraints will adjust as necessary.
•Clear the Distance 
check box to define the constraint as a driven constraint.