What's the difference between balancing columns and aligning them?

We're currently on XPP 8.4.

Chapter 11 of styles.pdf contains a very detailed explanation of how the "Balance/Align Columns" setting affects the composition process, but I'm having a hard time understanding what the difference is at a high level. I have a two-column layout. I tried experimenting with my Pagination Style changing between "align" and "balance", and the output seems to be the same. On pages that are not completely filled, text is evenly distributed between the two columns. Why might someone use "align" instead of "balance"? Are there specific scenarios where one is more appropriate than the other?

On a related note, the description for "align" says:

Fills all columns equally, aligning the baselines of subsequent
columns with that of the shortened depth of the first column.

I'm familiar with the term "baseline" as it applies to a single line of text. What is the baseline of a column?