This statement is true. Reserved Instances offer a significant discount over On-Demand Instance pricing, which can be up to 75% depending on the term and payment options. Moreover, when a Reserved Instance is specified for a particular Availability Zone, AWS reserves capacity for that instance, ensuring that the user can launch that instance when needed in the chosen Availability Zone. Other options like Spot Instances can offer even more significant savings but do not guarantee availability, while On-Demand Instances guarantee availability but at higher costs without upfront commitments.