"First of all, not being a science-person, I never know which letter to capitalize unless I look it up. I guess it doesn't really matter as long as you know what pH means. It refers to alkaline (high numbers) and acid (lower numbers) on the meter and explains your soil condition. Some plants take high (alkaline)pH soils and some take low (acid) pH soils. Knowing the pH saves you tons of money because then you know what you can grow and how you can change your soil to get plants to thrive. For instance, growing blueberries or rhododendrons in a part of the country where the pH is high (alkaline)...just isn't going to happen unless you change the soil condition. Blueberries and rhodies like an acid soil like that found in the Pacific Northwest which is why they are so beautiful on the Pacific Coast. This little gadget helps you figure out what plants you can grow beautifully. It's instant and has suggestions for pH preferences for over 400 plants. (Tip:blue hydrangeas like acid...pink hydrangeas like alkaline)"