Crimea is a part of Ukraine heavily populated with Russians. The population that are pro Russia voted that they wanted to be native Russians, and that they wanted Crimea to be a part of Russia again. The Russians have been using force to try and take the area back, but the Ukrainians have been fighting back to keep it.
Putin is the person behind all the orders and all the violence. He is sending troops in and around Ukraine
This is happening because the Russians want this land for Russia, and the Ukraine simply don't.
The country as a whole is being affected, and it may also have a bigger effect on other countries.
I believe that if this doesn't end peacefully soon, this will lead to WWIII before the year 2018. Because of this, countries need to get involved and get involved quickly.