Point tweaking is moving or setting keys on the individual points of an object. When you tweak the points of an object for which you have already created some deformers, Maya automatically prevents the unexpected effects that can occur when you use deformers. Maya does so by applying the tweaks to the object before applying any deformations to the object.
When you create deformers, Maya creates tweak nodes as well as deformation nodes. In the dependency graph, Maya places the tweak nodes as inputs to the deformation nodes so that any point tweaking is carried out before the evaluation of the deformation nodes. This placement means that, by default, an object’s deformation order includes point tweaking first, and then includes deformations in the order that the deformers were created.
You should avoid changing the number of a deformable object’s points (for example, CVs, vertices, or lattice points) after you create a deformer. Changing the number of points can lead to unexpected deformation effects. Be sure you are happy with the deformable object’s topology before you begin using deformers. You can save a copy of the object in case you want to do further modeling in the future.
When the deformation order includes point tweaking first (the default), CVs may not move in the same direction as the Move Tool’s manipulator if the attributes of the deformers do not have their initial (reset) values. If you would like to change this, reset the deformers to have their initial (reset) values. Alternatively, you can change the deformation order so that Maya applies the point tweaking after applying deformations. However, if Maya applies point tweaking after applying deformations, you may get unexpected results when you use the deformers.
If you do some point tweaking and then want to check how the object deforms without the tweaking, you can disable the tweak node.