Kratom is a type of tree, also known as Mitragyna speciosa, which is native to Southeast Asia. The leaves from this tree have been used for centuries for their traditional medicinal properties and ritualistic healing.
Kratom is used for many reasons, including:

• in low doses as a energizer
• in higher doses for full body relaxation
• euphoric enhancement
• sexual prolonging

Kratom can be chewed, smoked, made as a tea, or taken in capsule form.  Traditionally, Kratom leaves were chewed by farmers and the working class of Southeast Asia.  In America, Kratom is most commonly taken as a tea or as a capsule.
Yes, Kratom is legal in the United States and Europe. Only a few countries have banned Kratom use, such as Thailand, which made it illegal in 1943. However, it is widely understood that this is an outdated law that was more about fixing the Thai economy during the East Asian War. Today, Thai officials do not vigorously enforce this law.  Similarly, Indiana has banned 2 alkaloids of Kratom, but not the plant itself.
No, Kratom is not classified as an opiate.
There is no evidence showing any overdoses resulting from Kratom use. When used excessively, you may experience an upset stomach.
No, Kratom does not contain any banned substances found on a drug test.