Separators (also called Spacers) are tiny circular objects or springs that your Orthodontist places between your molars. They prepare your teeth for braces by creating a small space between your molars where metal Molar Bands will later be placed. If your teeth are not very crowded, you might not need spacers before your braces go on.
Separators can be uncomfortable and annoying because it feels like you have something stuck between your teeth (and in fact, you do)! Fortunately, you will only need to wear them for a few days. When your braces are put on, the Separators are removed.