It is easy. In a conventional program the developer is obliged to define all the ways the program could follow during its life to solve the problems. And there may be thousands, tens of thousands or...
You must use Lisp or ProblogOr, for non computer scientists, an "expert system generator" who allow you to program in everyday language (T.Rex for example, a reasoning tool).
To date, there really is no difference. Artificial intelligence is just a regular computer program designed to make a computer seem to "think" like a human does. Artificial intelligence may include...