Before judging difference it is important to know what is ‘Yoga’? Yoga is a sanskrit word which means intentional and concentrated practice to unite one’s ‘Atma’ in ‘Paramatma’. Atma means spirit and parama means supreme. Paramatma is the name given to supreme energy in snskrit. This yoga is practiced mostly by Indian saints known as yogis. To keep them selves concentrate on yoga, yogis used to keep themselves fit physically and mentally. For that they used to practiced ‘Asanas (postures)’ which keep the phisical and mental bodies fit and healthy by which yogis used to not get disturbed by ill health and other problems.
But in modern days the word yoga is misunderstood by people. The asanas were understood as yoga by people and practicing asanas with the name yoga. These days many people are practicing ‘yogasanas’ only but not yoga.
Meditation is also one kind of yoga practiced by saints in west. But these days meditation is understood as excercise to maintain mental balance and relaxation from stresses.