One (of many) reasons you may get two W-2's from the same employer, would be if you earned income from that employer in more than two states that tax your earned income. Since the W-2 only has blocks to report income to two states, they would issue a 2nd W-2 showing the information for the 3rd and/or 4th state in those blocks. You treat it "AS IF" you received one physical W-2, with all 3 or 4 states on it.
This would be true also, if the employer had more than four entries for block 12.
