Tokens are the placeholders in the URL. Each platform names there placeholders differently. Placeholders are basically vacant seats that are ready to accommodate data. When visitors click through the ads, lander and offer, their clicking data is assigned to the placeholders (vacant seats). We just need to know how each platform names their placeholders, the data held in the placeholders can be passed back and forth freely.
Each time after a visitor clicks on the URL, the tokens will be filled with data.