Temporary email is most useful when you want to receive a one-time verification message, test a website, download a resource without giving your primary address, or reduce promotional mail. It can also help developers test registration and notification flows. It should not be used to bypass security controls or to operate accounts that require reliable long-term recovery.
For practical use, always review the provider rules and avoid sharing sensitive information through temporary inboxes. A temporary address is best suited to low-risk, short-term interactions.