On Monday, Vladimir Putin will again become president of Russia. When he is inaugurated in the Kremlin, it will be for a third term, even though the Russian constitution limits presidents to two four-year terms.
The restriction, however, is for two consecutive terms. It doesn't rule out a third term if someone else holds the presidency in the interim. That's exactly what Dmitri Medvedev did. He was elected president after Putin, but declined a run for a second term.
This political swap succeeded, but Putin will be leading a different Russia after his re-inauguration.