Keep Together - Save Space & Paper, or Keep Questions Together
Keep Together is a question and design item option you will find in Design View. This option is one that can help save space and paper when formatting a test document; or that can help with the readability of items such as questions and instructions.

Here's an example of how it can work. With the sample Geology test open, I can open Design Edit and quickly see that all of the questions are set to Keep Together:

When I check out the layout of the test in Document View, there is one lone question on page 3; a waste of paper and ink if I need to print 30 tests.

I return to Design View and open Design Edit again. I uncheck Keep Together for all questions and Apply that change to all the questions.

Now in Document View there are only two pages:

But there is a trade-off, one question carries over two columns and one question carries over both pages:

If saving paper and ink are important, the readability trade-offs might be acceptable.
One tip to keep in mind: Keep Together is set individually to questions and other design items so you can use Keep Together with some questions but not with others. When working with a wider variety of questions and text in a test, Keep Together can be used effectively to balance out readability and space savings.