What's the difference between Layers and Criteria?

A Layer is a single stratum in the dw-2000 Layout Editor drawing space. dw-2000 supports 256 discrete Layers, each of which can be viewed, color coded and extracted separately. dw-2000 Criteria are descriptive names that can be assigned to one or more Layers and/or Types of Elements in the Library. Criteria are especially useful when creating multi-layer components, since they allow you to give meaningful names such as "Metal" or "Poly" to particular Layers or Types of data.