Machining:
Machining is any one of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process.
General machining processes, include boring, drilling, turning, milling, broaching, sawing, shaping, milling machines, drill presses, planing, reaming, and tapping. Machine tools, such as lathes, turret punch presses or others, are used with sharp cutting tools to remove material to achieve a desired geometry.

Forming:
The forming process makes use of suitable stresses like compression, tension, shear or combined stresses to cause deformation of the materials to produce required shapes. In forming, no material is removed, i.e. they are deformed and displaced.
There are many varied methods of forming used, one common method is roll forming. Roll forming, roll bending or plate rolling is a continuous bending operation in which a long strip of metal is passed through consecutive sets of rolls, or stands, each performing only an incremental part of the bend, until the desired cross-section profile is obtained. Roll forming is ideal for producing parts with long lengths or in large quantities.