Giving an acknowledgment is a way of giving credit or props. Acknowledgments let you know who contributed or did work on something.
If you look at the acknowledgments section of a book, it tells you who helped the author: writers give acknowledgment to editors, agents, friends, family, teachers, people they interviewed, and anyone else who helped them while writing. In sports or the entertainment world, award-winners usually give acknowledgment to people important them. When you see the word acknowledgment, think "giving credit and thanks".