Sestinas are 6x 6 line stanzas containing 6 end words, plus a three line ending called an envoi, and you could be forgiven for thinking they're a type of word game in terms of form. The stanzas all contain particular end words, which are used as a group in a 3 line ending being the envoi. This is tougher than it looks, and the patterns vary considerably, because of the size of the poem, which is 248 words.
Examples of Sestina:
|For example, the six end words are apple, orange, cherry, oak, willow, rose, 123456|
Each stanza uses the six words as
615243 (a standard sestina technique)
615243 would be rose, apple, willow, orange, oak, cherry.
The envoi will include all six words.