Lean vs Six Sigma
In essence, Lean and Six Sigma methodologies have essentially the same objective. Both want to eradicate waste and develop the most effective process or system they can, however they use their own methods on how they achieve this objective. Essentially, the main distinction between Six Sigma and Lean is they determine the root causes of waste in different ways.
Lean practitioners have the belief that waste originates from needless steps in production processes that don't add any value to the end product, whilst Six Sigma advocates maintain that process wastes result from variations within processes.
Needless to say, both of these determinations are true, which is the reason both Six Sigma and Lean methodologies are generally so effective in maximizing business overall performance in a wide variety of areas. In actual fact, these 2 methodologies have been found to be particularly effective when working in conjunction with each other - thus the advent of Lean Six Sigma.