Modern materials are developed through the invention of new or improved processes, for example, as a result of 'man' made materials/ingredients or human intervention, in other words not naturally occurring changes. They are altered to perform a particular function. Many smart and modern materials are developed for specialised applications but some eventually become available for general use.
Smart materials respond to differences in temperature or light and change in some way. They are called smart because they sense conditions in their environment and respond to those conditions. Smart materials appear to 'think' and some have a 'memory' as they revert back to their original state. The term 'smart' can be ambiguous as in some cases it is difficult to distinguish between modern and smart.