The reverse reaction to Diels-Alder is called retro-Diels-Alder. Diels-Alder adducts decompose on heating into the diene and dienophile that formed them.
The bonds formed by Diels-Alder (red) break, leaving free diene and dienophile.
In the case of adducts formed from alkynes, it is possible to break the molecule in two different ways, choosing the one that leaves the attracting substituents on the dienophile.
