The Platt Amendment
After the US military government left Cuba, a Constitution was formed.  It gave in to the Platt Amendment, which let the US intervene in Cuba when it wanted and lowered tariffs on US goods.

The Original Blockade/Embargo
After the failed Bay of Pigs attack, the economic aggression the US displayed towards Cuba was strengthened.  It prevented goods from being traded between Cuba and the US.

The Torricelli Act
The Torricelli Act became law in 1992.  It tightened the embargo by stopping the flow of food and medicinal goods to Cuba.  The only exception is humanitarian aid.

The Helms-Burton Act
Signed into law after the Brothers to the Rescue planes were downed, this law sought to tighten the embargo on Cuba.  Though it has caused great suffering in Cuba, it had the unintended effect of strengthening Castro's popularity in Cuba because it allows him to blame all of Cuba's woes on the US.