Here's a breakdown:

* Chromatids: These are identical copies of a single chromosome, formed during DNA replication.

* Centromere: A specialized region of DNA that serves as the attachment point for spindle fibers during cell division. It's a constricted region on the chromosome.

Think of the centromere like a "glue" holding the two chromatids together. During cell division, the spindle fibers pull on the centromeres, separating the chromatids and ensuring each daughter cell receives one complete copy of each chromosome.