Hi notso
Mini I will attempt to explain the ketosticks, but you might get a more reliable explanation by googling.
Basically, if you eat carbs, your body burns them first, and also stores energy as glycogen in your muscles and liver. Any excess sugar is converted to fat by insulin.
If you reduce carbs, your body uses up the stored glycogen, then turns to the energy which is stored as fat - so your body becomes what is called 'ketogenically adapted' which means it is capable of burning fat directly. A byproduct of ketogenesis (the burning of fat) are what are called ketones, which are excreted in your urine, and what ketosticks detect.
You pee on a ketostick, and depending on the level of ketones, will show up as light pink to dark purple.
The only thing, is that there is a negative feedback loop with ketones. If you body detects too high a level of ketones, it will perceive a food shortage, and stop burning fat. That is one of the reasons why it is a good idea to drink lots of water on this WOE - to flush out the ketones and fool your body into continuing to burn fat. If you are drinking sufficient water, the ketosticks should only show as light pink.
Disclaimer - these are ketosticks as I understand them - some of it may be completely incorrect.