What are the 3 main differences in arteries and veins
Arteries differ from veins in that they most often carry oxygenated blood away from the heart and into the rest of the body system. The function of arteries and veins differs in that arteries do not have valves, except for the pulmonary artery. Another difference between arteries and veins is that veins are typically located closer to the skin’s surface than arteries.

How are arteries and veins similar
Veins and arteries play a major role in circulating blood. They work together to develop a cycle that transports blood from the heart, transferring oxygen and other minerals to the organs and bringing back deoxygenated blood. Arteries and veins consist of various layers of cells that maintain the structure. These vessels are flexible and provide nutrients to the body.

Why are veins thinner than arteries
Veins have thinner and less muscular walls. This is because veins have a lower level of pressure than arteries. So, their walls don’t need to be as thick to handle the pressure. Veins can widen (dilate) as the amount of fluid in them increases.

Are veins bigger than arteries
No, the veins are thinner and less stretchy. This structure helps veins move higher amounts of blood over a longer time than arteries. Generally, arteries are larger in diameter than veins. This is because they need to be able to accommodate the high volume of blood being pumped out of the heart

What are the two types of veins
Pulmonary veins. The pulmonary circuit carries deoxygenated blood from your heart to your lungs. Once your lungs oxygenate the blood, the pulmonary circuit brings it back to your heart. There are four pulmonary veins. They’re unique because they carry oxygenated blood. All other veins carry only deoxygenated blood.
Systemic veins. The systemic circuit carries deoxygenated blood from the rest of the body back to your heart, where it then enters the pulmonary circuit for oxygen. Most veins are systemic veins.

Sources:
https://www.ncbi.nlm.nih.gov/books/NBK547743/

Artery vs. Vein: What is the Difference?

Veins & Arteries Similarities And Differences

https://my.clevelandclinic.org/health/body/23360-veins
https://www.webmd.com/heart/difference-between-arteries-and-veins
https://www.healthline.com/health/venous-system#types-of-veins