Each side of the heart has two parts, the atrium and ventricle. The atrium is where blood enters that side and the ventricle is where blood exits that side.
Now that you are familiar with those terms. The right side of the heart (or left if you were looking directly at someone and starring at there chest) is the side of the heart where blood flows into from the rest of the body. Blood is then pumped from the right side of the heart to the lungs where it drops of CO2 and picks up oxygen.
Once blood is oxygenated, it flows to the left side of the heart into the left atrium. The left ventricle then pumps blood to the rest of the body through the aortic artery ( a huge artery