Sides of the conflict:
This situation separate the country in two sides: one side that support Russia and believe in the join between them or the other side than support Europe. Ukraine is in economic crisis so they need help of Europe or Russia. Yanukovich was the president and he takes refuge in Russia.
Russia takes action
In the south of Ukraine, Crimea, lives a population of Russian origin who disagree with the pro-European ideas. Then, Putin decide send special troops and take control of Crimea, President obtained permission from Russian parliament to intervene militarily in Ukraine, this triggered a referendum which resulted in 96 percent of the population in favor of joining Russia.
USA and present
The conflict began peacefully but since Russia's entry numbers of deaths and injuries has grown and the most of the population are armed. Obama has warned Putin that if he continues that way Russia will apply sanctions. Today, a new President Alexander Turchinov, which later will be changed by Petro Poroshenko. There was an important event that was the downing of the plane of Malaysia Airlines for a missile supposedly pro-Russian side. A truce was signed but still small clashes that can break this truce.