BeforeAll vs. BeforeEach. When to use them?

I was recently looking over a co-workers code and I realized that he implements a jest function in a BeforeAll function at the top of the describe call, and then creates a data object in a beforeEach function. This made me wonder, what exactly are the differences between BeforeAll and BeforeEach.

It was time... I went to Google!! I did find some articles that helped shed some light on some of the functionality differences between the two.

Findings 1: http://breazeal.com/blog/jasmineBefore.html

Findings 2: Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

Given the articles I found that BeforeAll is called once and only once. While the BeforeEach is called before each individual test. Which was great! I now had a better idea of when it was being called!

I also found out that the BeforeAll is best used for initializing code. Which makes perfect sense! Initialize it once. Boom, you're done.

My confusion I am having is when is something initialized and when is it not? I have found that BeforeEach in our code is used more often than not. What I am curious about is what kind of code is considered to be "initializing" code, vs whatever code should be in the BeforeEach.

An example from our code below:

    beforeAll((done) => {
      // Mocking method from within Box file
      transferBoxPlanSpy = jest.spyOn(Box, 'transferPlanFromBox').mockImplementation(() => Promise.resolve());

      // Pulling data from MongoDB
      User.findOne({ user_name: 'testsurgeon1' }, (err, user) => {
        user.addMGSPermission();
        user.save(done);
      });
    });

    beforeEach(() => {
      planData2 = {
        user_name: 'hello1',
        laterality: 'right',
        plan_id: 'testplan42',
        order_number: '856-hd-02-l',
        file_id: '123456sbyuidbefui',
      };
    });

I hope my question isn't too vague. Thank you for your time!