I'm reading about sets and see terms like "specific" elements and "arbitrary" elements. For example:
"The method remove removes a specific element from a set; pop removes an arbitrary element".
Can someone explain arbitrary elements?
ˈärbəˌtrerē/adjective, based on random choice or personal whim, rather than any reason or system.
In the context of your question, "arbitrary element" simply means an element not chosen by you. From the program's perspective, the element was chosen randomly and unpredictably.
x = set([1,2]).pop()
x might have the value
2, but you cannot predict beforehand which one it will be.