Veins

Veins carry blood under low pressure to the heart.  he veins have thin elastic walls. 

 Because of a thin wall there are valves forcing the blood to flow one direction only!

Arteries

On the other hand, arteries have thick elastic wall and it carry blood away from the heart.  These elastic walls contract strongly forcing the blood to move and this is what we call pulse.  It can be found very deep in the body tissue. 

Capillaries

These are the small vessels which connect the artery to the vein.  The thin wall allows gasses to diffuse through it.