What can ancestry tests tell you?

Can ancestry tests help me reconnect with long lost relatives?

Ancestry tests can tell you about what areas of the world your ancestors originated from.
Because of interrmariage that occured throughout history, no one is 100% of anything.
You can compare your DNA with others. Depending on how much DNA you share with them, a possible relationship could be estimated. Most of the companies offering ancestry tests have DNA databases as well.
You can also find out, for example, what procent of your DNA is African, or from Northern Europe, or Native American.