Inulin is a type of complex carbohydrate present in Agave plants and the key component of why it is possible to ferment Agave into alcohol - and then distil it into Tequila!
Understanding what it is helps make sense of the Tequila production process too, whose first step is to roast the Piñas. The cooking process (also known as saccharification) hydrolyzes inulin into fructose. The next part of the process is to mill the cooked agave to extract the sugars, then ferment it to convert the sugars into ethanol before a two-step distillation process begins.
Without inulin, there would be no fructose, and nothing to use to ferment and convert into alcohol.