Whats the comparison and contrast between arteries and veins?

"Arteries are blood vessels that carry blood away from the heart (as opposed to veins, blood vessels carrying blood toward the heart)."

Also, arteries tend to have thicker walls because of more muscle surrounding them.

Similarities:
1) Blood vessels

Differences:
1) Artery carries oxygenated blood (light red) but vein carries deoxygenated blood (dark red).
2) Artery carries oxygenated blood from heart to other organs but vein returns deoxygenated blood from organs and other parts of body to heart.
3) The pressure of blood in an artery is higher than in a vein.

The comparison is that they all carry blood.
The contrast is that the arteries carries oxygenated blood except the pulmunary artery whilst the veins carries deoxygenated blood except the pulmunary vein.

because of the different functions said somewhere up there ^ by another contributor, they need to have different structures
The arteries obviously need to withstand higher pressures (known as hydrostatic pressure when it forces small soluble molecules into the capillaries) this means that when they expand due to great pressure they musn't tear, so the arteries contain elastic fibres in all the layers of their structure. In the tunica intima it is made up of endothelium cells and elastic fibres, in the tunica media it is made up smooth muscle (for strength), elastic fibres (for expansion) and collagen fibres (for strength and support). The tunica externa is made up of elastic and collagen fibres.
On the other hand, the veins don't have to withstand anywhere near as much pressure so dont require as much elastic fibres, though still have a few in the tunica media along with smooth muscle, the tunica externa only contains collagen fibres really, just providing support and structure, the tunica intima is just made up of the endothelium.
The veins also may need a little helping hand if there really isnt hthat much blood pressure (during diastole) so have got valves in them (them swooshing the blood back to the heart is what makes the pulse sound in your wrist etc).
Other than their functions they are the only major structural differences
This as im sure you can tell has not been copied and pasted form anywhere so Hope this helps!

arteries carry nonoxygenated blood to the heart, and veins carry oxygenated blood away from the heart to the rest of the body

The basic definition for arteries is, arteries carry blood away from the heart and almost all of them except the Pluminary and Umblical cord artery carry oxygenated blood. Pluminary arteries carry deoxygenated blood because they take deoxygenated blood from the heart to the lungs.
Since arteries take blood away from the heart, the blood has higher preasure and arteries hence have thicker walls when compared to veins

Veins on the other hand, carry blood away to the heart and almost all of them except the Pluminary and Umblical cord vein carry deoxygenated blood. Pluminary veins carry oxygenated blood because they take oxygenated blood from the lungs to the heart.
Since veins take blood to the heart, the blood has lost it's pressure and  veins hence have thinner walls