The referendum of December 12th, 1993 approved the Constitution of the Russian Federation. The new Basic Law of the country proclaimed Russia a democratic, federal state based on the rule of law and on the principle of separation of powers between judicial, executive and legislative branches of power.
The Constitution, however, reserved a leading role for the executive power, namely the President, making Russia a presidential republic. For a complete list of presidential powers and duties follow the link.
According to the Constitution, "No one person shall hold the office of President of the Russian Federation for more than two terms (4 years + 4 years) in succession." However, the Basic Law does not prohibit the same person to run for the third time at a later time.
On the subject read also:
On the history of the constitution question in Russia in the 20th century, CDI Russia weekly