Here is the definition for Correct Law (from the Soka Gakkai Nichiren Buddhism Library Glossary):
Correct Law (Ch zhengfa, J shōhō or shōbō) An abbreviation for the period when the Correct Law prevails. According to Buddhist belief, after the death of a buddha, his teachings pass through three periods or phases of development. In the first, known as the period of the Correct Law, Buddhism is a living religion and those who practice it attain enlightenment through its teachings. The period of the Correct Law following the death of Shakyamuni Buddha is usually said to have been a thousand years in length, though some sources describe it as five hundred years long.
And here is the definition for Counterfeit Law:
Counterfeit Law (Ch xiangfa, J zōhō or zōbō) Second period following the death of a buddha. During this period, Buddhism becomes increasingly formalized, people’s connection with it weakens, and progressively fewer of them are able to gain enlightenment through its teachings. Some sources describe the period of the Counterfeit Law following Shakyamuni’s death as a thousand years in length, others as five hundred years.