What is a triolet?

Made by Katherine

A (first line)
B (second line)
a (rhymes with first line)
A (repeat first line)
a (rhymes with first line)
b (rhymes with second line)
A (repeat first line)
B (repeat second line)

The summer weighs us down with sullen  heat
Even cats and dogs  sit still as stones
Gone are early flowers with fragrance sweet
The summer weighs us down with sullen  heat
The hot flagstones return my angry beat
As people  scurry by ears to their phones.
The summer weighs us down with sullen  heat
Even cats and dogs  sit still as stones