The consumption-based model is a billing approach where users pay only for the resources they consume, such as storage, processing time, or bandwidth, rather than paying for hardware or software licenses upfront. This model offers flexibility and cost savings since users are not required to invest in their own computing infrastructure and can scale their usage up or down according to their needs. Fixed cost models, while they can exist in some cloud scenarios, typically involve a predetermined fee regardless of the actual usage, which is not the essence of the consumption-based model. Sliding scale and free trial are not billing models associated with regular cloud service consumption.