Point tweaking skin objects refers to moving or setting keys on the individual skin points of a skinned object. When you tweak the points of a skinned object, Maya automatically prevents the unexpected effects that can occur when you manipulate the object. Maya does so by applying the tweaks to the object before applying any deformations to the object.

When you bind skin, Maya creates tweak nodes as well as nodes for the skinned objects. In the dependency graph, Maya places the tweak nodes as inputs for the smooth skin objects so that any point tweaking is carried out before the evaluation of the smooth skin nodes or rigid skin nodes. This placement means that, by default, a skinned object’s deformation order includes point tweaking first.

If you prefer, you can change the deformation order so that point tweaking does not occur first. See Change a skinned object's deformation order.

Also, if you do some point tweaking and then want to check how the skinned object deforms without the tweaking, you can disable the tweak node.