The "intertestamental" (or "between the testaments" or Second Temple period) period is the time between the final writings of the Old Testament and the arrival of Christ. It lasted from the period of the prophet Malachi (about 400 BC) to the preaching of John the Baptist (about AD 25).
Some refer to the period from Malachi to Matthew as the "400 silent years" since there was no prophetic message from God during that time. During this time, Israel's political, religious, and social climates altered dramatically. The prophet Daniel foresaw much of what happened.
This is a fascinating period rarely taught in any churches, full of political intrigue (both internal and external) and Jewish persecution. It had a significant impact on the Jewish people. Control of the land and the Jewish people passed from one governmental force to another throughout these years, including Persia, Greece (Alexander the Great), Egypt (the Ptolemies), Syria (the Seleucids), and the Maccabees (and the Hasmoneans).