What is the main difference between cardio and strength-training activities?

One of the main difference between cardiovascular endurance (training) and Strength Training is Cardio challenges the pumping and amount of blood that is constantly being supply to your muscle, while strength training challenges your muscle capacity to lift an object (weight). You can refer Cardio as heart or the Circulatory System and Strength for muscles. 
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Air goes past the epiglottis and into the trachea when you breathe in. from there, it goes to your vocal cords in the larynx until it reaches the bronchi. from the bronchi, air passes into each lung.