Warp Model
The default warp model is Helmert for the first invocation of the MultiPoint Warp command. The last used model becomes the next default model. The Warp Model dialog box setting automatically changes the associated ribbon bar setting, and viceversa
Resample
The default is unchecked. When Resample is unchecked, the Warp command is display only, meaning that warp settings are applied only to the image display and are not saved. This takes less time and is useful for viewing and printing. When Resample is unchecked, Helmert and 1st Order Polynomial are the only two Warp Model options available.
When Resample is checked, warp settings are applied to the image itself when you save it. When checked, there are three Warp Model options available (Helmert, 1st Order Polynomial, and Projective).

Helmert  This model, sometimes referred to as an Orthogonal warp, performs a general data file rotation, X and Y axes translations, single value scaling, and orthogonality of perimeters. This warp is proportional and cannot be "rubber sheeted". The minimum number of points is 2, and will also create residuals if more than 2 point pairs are selected. In effect, the Helmert warp operates more like an interactive scale and rotate function. No distortion is created with this method. General use includes engineering type applications.

1st Order Polynomial  This model uses a first order polynomial to mathematically best fit the data. This is the stereotypical "rubber sheet" warping. A minimum of three point pairs will ensure that the source/destination points are placed exactly, while other portions of the drawing will be placed as close as mathematically possible.
With 3 point pairs, there will be no residuals (errors). 
Projective  Projective warping will determine exact placement of 4 control points (corners). Although this warp is categorized as a Linear warp, second order polynomials are used to determine the location of the fourth point. This model eliminates the "best fit" results of Affine warping when applied to rectangular data. While accuracy of the fourth point is substantial, the time required to calculate results using this model is also substantial an may deter use with large data sets.
Points
Automatically updates with the appropriate number of points as different warp models are selected. You cannot edit this field, however you can collect as many points as you desire (over the minimum required) for any warp model.
Point Number
Displays the Source and Destination point pairs. When you place your first set of points (Source/Destination), it is considered to be point number 1 (point pair). The second set is point number 2, and so on.
Source (in)
Displays the X and Y value for each Source point. The values are displayed in inches.
Destination (wu)
Displays the X and Y value for each Destination point. The values are displayed in working units.
Residual
Displays the X and Y value for each point's residual error. The residual error for each point pair represents the error involved in modifying the Source point to its corresponding Destination point.
Mean square error
Displays the measure of how well the transformation model selected fits the point pairs defined. It is the average of the individual point errors (divided by the Degrees of Freedom).
Delete
Allows you to delete a point pair from the points window. When a point pair has been defined and highlighted in the points window the Delete button is enabled. Selecting the Delete button causes the highlighted point pair to be removed from the points window, and all the remaining points will be reassigned the next number available (incremented by 1 or however many point pairs were deleted). For example, if you have 3 point pairs defined, and delete point pair 1, point pair 2 becomes the new 1, and point pair 3 becomes 2. If you collect another pair, it becomes point pair 3.
You can delete multiple point pairs with the Delete button. After highlighting the first point pair to be deleted, holding down the Ctrl key allows you to select any combination of other point pairs. Holding the Shift key selects all the point pairs from the first one highlighted to the second one. This works exactly like selecting files in Windows Explorer.
Load
Allows you to load previously defined point pairs. Selecting this button displays the Load Points Dialog Box.
Save
Allows you to save the currently collected points shown in the points window to a file on disk. This allows you to reuse the defined point pairs for future warps. Selecting this button displays the Save Points Dialog Box.
To use this functionality, you must install the Image Integrator option.