Arteries are quite tough on the outside, with a smooth inside so that the blood can flow easily with no obstacles and a very strong elastic muscle in the middle. So with every heart beat, the artery expands as it fills with blood, and when the heart relaxes, the artery contracts, forcing the blood along through the circulation system. You can feel your artery expand and contract, feel for a pulse in your wrist or neck. Since arteries keeps pace with the heart, we can count the heart rate by counting the contractions in the arteries, and that's called, taking a pulse. Capillaries are embedded in tissue, they allow the exchange of gases within the tissue.
Capillaries are very thin and fragile and are only one epithelial cell thick.
The exchange of oxygen and carbon dioxide takes place through the thin capillary wall. Red blood cells inside the capillaries release their oxygen into the surrounding tissue. The red blood cell well then take up waste products, like carbon dioxide, which is released by the tissues. Waste rich blood moves from the capillaries to the veins. Because arteries and veins run parallel to each other, they a connected via capillary networks running between them.