It’s the destructor, it destroys the instance, frees up memory, etc. etc.
Here’s a description from ibm.com:
Destructors are usually used to deallocate memory and do other cleanup for a class object and its class members when the object is destroyed. A destructor is called for a class object when that object passes out of scope or is explicitly deleted.
See https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_74/rzarg/cplr380.htm