Aligning the text to the baseline is a common practice for multi-column page designs, like magazines. It makes the text baselines align across columns. So, if you put a ruler on the page at the baseline, they would all line up across columns. This makes for a much cleaner look.
You need to know your leading size to start with. Go to Preferences > Grids, then change the Increment Every number to match your leading value. Once that’s done, go to Indents and Spacing in your paragraph style. Set Align to Grid to All Lines.
- Adobe: Aligning Text