Final answer:
On-demand scalability is a cloud computing feature that allows users to request additional space and have the provider allocate additional resources seamlessly to the end user.
Step-by-step explanation:
The cloud computing feature through which users can request additional space and the provider allocates additional resources seamlessly to the end user is On-demand scalability. On-demand scalability allows users to easily scale up or down their cloud resources based on their needs without any interruption. For example, if a user needs more storage space, they can simply request it from the cloud provider and the provider will allocate the additional space without any downtime.