A "renga" was originally a poem written by two people ("Partnergedicht"). The Wiki links on it are good, I think:
"Ein Autor schrieb drei Zeilen (5-7-5 Silben) vor, den sogenannten Oberstollen. Dann bat er seinen Dichterfreund um Vollendung des Verses, der aus zwei Zeilen (7-7 Silben) bestand, dem sogenannten Unterstollen."
http://www.haikulinde.de/Haiku/renga.htm"Poets worked in pairs or small groups, taking turns composing the alternating three-line and two-line stanzas. [...] In order for the poem to achieve its trajectory, each poet writes a new stanza that leaps from only the stanza preceding it. "
https://www.poets.org/poetsorg/text/renga-poetic-formCf:
https://www.youngwriters.co.uk/types-rengahttps://thewayofhaiku.wordpress.com/renga-cards/Examples of rengas:
http://www.renga-platform.co.uk/webpages/renga_02.htmI think this describes it well:
"The next poet takes inspiration from the previous stanza to compose their verse."
http://blog.asianart.org/blog/index.php/2009/07/02/poetry-is...Best