Russia has agreed to loan Venezuela $2.2 billion to buy more Russian weapons. This includes S-300 surface-to-air missile systems. S-300 battalions (also called the SA-20 in the West) consist of a radar unit, and 4-8 launchers (four S-300 missiles are mounted on each launcher, which is carried by semi-trailer truck).
Roughly equivalent to the U.S. Patriot, the Russian built S-300 was first known as the SA-10 to NATO, when the system first appeared in the late 1970s. Current S-300 missiles weigh 1.8 tons each and are 26 feet long and about 20 inches in diameter. The missiles have a range of some 200 kilometers and can hit targets as high as 100,000 feet. The missile has a 320 pound warhead.
The 64N6 radar used by S-300 battalions has a range of 300 kilometers. Venezuela has about 5,000 kilometers of borders, so at least five S-300 battalions would be needed. That would consume most of the $2.2 billion, depending on what model (some S-300 models are more expensive, and capable, than others.) The really high end stuff would be needed to have a chance against the United States, which is what Venezuela says it needs to defend itself from.
Venezuela is also said to be buying 92 tanks, either T-72s or T-90s (the latter is a much upgraded version of the former). None of Venezuela's borders are tank country, and only one of Venezuela's neighbors has large tank forces (Brazil, which has over 500 heavy tanks). So these tanks would mainly used to keep Venezuelans in line. For that, T-72s would do.
Venezuela has already purchased $4 billion worth of Russian weapons, mainly Su-27 jet fighters, and hundreds of thousands of assault rifles for a militia loyal to president Hugo Chavez. While Venezuela is a major oil producer, Chavez has been spending money faster than he can pump oil. An increasing number of Venezuelans are unhappy with the billions in oil revenue given to foreigners, or spent on weapons and cronies. Thus the importance of getting a loan (which may never be repaid, especially if Chavez gets overthrown). Chavez apparently is also seeking advice from the Russians on how to turn a democracy into a police state (which the Russians are currently writing the book on.) Chavez is in need of this kind of knowledge, because his growing clamp down on opposition media, and any opposition in general, is generating increasingly violent resistance.