Suits are normal formal wear in men's clothes. It consists of dress pants with a non clashing jacket. A dress shirt with a necktie or bow tie is worn under the jacket. A tuxedo is very similar but usually more fancy and worn for proms, weddings, or (very rarely) funerals. Some tuxedo jackets have coat tails and tuxedos often or worn with a vest over the dress shirt (the vest would still be under the jacket). Hope this helps!

To know about it refer this Damn sure you would know the difference and feel the difference.