This is an endzone play. It is typically done when the opposing team turns the disc near their own endzone.
Before the disc is called into play the handler will call "ISO [name] [name]". A cutter will drop back to act as a third handler. The cutters not called for the iso or to handle will move into the back corners of the endzone.
The two cutters called for the iso will work together to get open for the handlers throw.
Gratuitous celebration.