Salt was initially designed as a remote execution system to be used for gathering data normally collected by monitoring systems and storing it for later analysis. However, as functionality grew, so too did a need to manage the execution modules that were doing the heavy lifting. Salt states were born from this need and, before long, the engine that managed them had expanded into other areas of Salt.
A point of contention between various configuration management systems is the concept of declarative versus imperative configurations. Before we discuss Salt's take on the matter, let's take a moment to examine the two.
It may be easiest to think of imperative programming like a script: perform Task A and, when it is finished, perform Task B; once that has finished, perform Task C. This is what many administrators are used to, especially as it more closely resembles the shell scripts that have been their lifelines for so many decades...