keto sticks are the strips he's refering to. they are a staple in the Atkins diet. But a lot of people who work out and eat a lower carb diet, use them to see when their body is burning fat as an energy source.
Ketosis is really a shortening of the term lipolysis/ketosis. Lipolysis simply means that you're burning your fat stores and using them as the source of fuel they were meant to be. The by-products of burning fat are ketones, so ketosis is a secondary process of lipolysis. When your body releases ketones in your urine, it is chemical proof that you’re consuming your own stored fat. And the more ketones you release, the more fat you have dissolved.