From Poetry Wiki
Other types of tercet include an enclosed tercet where the lines rhyme in an a b a pattern and terza rima where the a b a pattern of a verse is continued in the next verse by making the outer lines of the next stanza rhyme with the central line of the preceding stanza as in Dante Alighieri's Divine Comedy. The tercet also forms part of the villanelle, where the initial five stanzas are tercets, followed by a concluding quatrain.
A tercet may also be separate halves of the ending sestet in a petrarchan sonnet where the rhyme scheme is abbaabba cdccdc as in Longfellow's "Cross of Snow." It also ends sestinas where the keywords of the lines before are repeated in a highly ordered form.