Basics

The Removal of Surface Contaminates from Parts
Although it can be as simple as "wiping something down" or rinsing something off, this typically refers to the practice as a part of a Quality Control Plan / Lab Protocol
Certain processes are more sensitive to surface contamination than others
- Painting, Powder Coating , and Electroplating are suseptible despite not being that "high tech" of processes
- Microfabrication and Micribiology are so sensitive that they must be preformed in Cleanrooms etc
Note that when cleaned to very high levels, Flash Rusting becomes a concern with certain metals, and thus either there should be little gap between the cleaning process, and the next manufacturing step, or special precautions should be taken, such as applying a temporary Gumming Solution

Methods

Scrubbing/Wiping etc
- Can get rid of "bulk contamination" ; still leves behing a thin film or best case scenario a Monolayer
- Thus it will still fail the Water Break Test
Media Blasting
- Can clean off stubborn contamination and even get to a level passing the Water Break Test
- Short of Dry Ice Blasting , it is an Abrasive process and thus has impacts on surface finish, and can not be used on thin parts
Surface Preperation (Surface Prep) for Painting etc is essentially this

Dissolves Contaminants
Polar for Polar Molecules, Nonpolar Solvents for Nonpolar Contaminants
- Most dirt and grime is nonpolar, hence most Cleaning Solutions focus on this, water works well otherwise in many cases
Misc Scales for "Solvent Effectiveness" although the nuance of each job makes these only marginally useful
- Kauri-butanol value
Note that even with a Perfect Solvent, Flow and/or Mechanical Action is needed to remove the Solution of Dirt+Solvent before it Evaporates
Processes like Spraying or Vapor Degreasing increase the effectiveness of solvents especially
Dry Cleaning processes such as using Supercritical CO2 are also in this category, more complexity, but more gentle on certain materials

Certain Cleaning Solutions can be used to turn Residues that won't dissolve, or be scrubbed off into other chemical compounds that can be
For instance, Bleach can react thin Hydrocarbon Layers allowing the underlinging material to pass the Water Break Test
- Even Comet Cleaner works quite well for technical applications!
Various Acids, and Pirranah Solution among other things also fit in this category