A setlist is a plain text list of the songs in playlist order, with their keys, which is exactly what a bandleader hands round before a gig.
On iPhone, iPad, and Android, tap the playlist, tap Share, then choose Setlist and send it to your bandmates. On Mac, click the playlist and then the Share button at the top right, or right-click the playlist name, and choose Export Playlist > Setlist. On Windows, right-click the playlist and choose Export > Setlist. On both desktops the list is copied to your clipboard, ready to paste into an email.
The same Share menu will also send the whole playlist in iReal Pro format, or as a PDF booklet of every chart in it.
For more, see Organize your songs into playlists on the iReal Pro website.