The Coda symbol shapes a song's form in two ways.

 

As an outro or tag. Placed in the form with a matching Coda section, the player takes the Coda only on the final repeat. With a Coda section but no symbol in the form, the repeats play in full and the Coda is added once at the end.

 

As part of the form. Pair the Coda symbol with a D.C. al Coda or D.S. al Coda text indication so the Coda plays through the repeats.

 

For the full explanation with chart examples, see How the Coda symbol works in iReal Pro on the iReal Pro website.