Both the Sadducees and the Pharisees were religious parties in Jesus' day. Both were critical of and were criticized by Jesus.
The Sadducees thought of themselves as "conservatives," as the Old Believers. This is because they accepted only the written Law of Moses as authoritative and rejected subsequent revelation. As a result, the Sadducees denied many of the doctrines held by the Pharisees and by Jesus, including the resurrection of the dead, the existence of angels and spirits, and the meting out of rewards and punishment after death. These beliefs were thought by the Sadducees to be Zoroastrian corruptions of the authentic faith of Israel.
Although a religious party, the Sadducees were more important as a political force. They represented the priestly aristocracy and the power structure of Israel. For them, the duties of religion centered primarily around the Temple.
The Pharisees, on the other hand, were a lay group more representative of the common man. In addition to the written Law of Moses, the Pharisees accepted as authoritative the rest of what is for us the Old Testament, as well as the "tradition of the elders."
Whereas the Sadducees saw worship at the Temple as the main focus of the Law, the Pharisees believed this to be but one component among many of proper Mosaic observance. It was over the interpretation of the Law and which understanding of it represented the authentic tradition of Israel that Jesus and the Pharisees disagreed.
After the destruction of the Temple in A.D. 70, Sadducaic Judaism disappeared and Pharisaic Judaism became dominant. It is from the Pharisees, then, that contemporary Judaism is primarily descended.