Recovery Point Objective (RPO) is measured in time, of how much data is potentially lost based on the frequency of your backups.
Recovery Time Objective (RTO) is also measured in time, of how fast you are able to restore services after disruption occurs.

RPO and RTO are both important metrics in determining your backup strategy. A successful and cost-effective strategy requires you to understand what kind of data each backup task is protecting, and the importance of it.

For example, while family photos and videos are things you can't ever replace, you can probably accept a temporary inability to access them. For this, you will need a low RPO but can tolerate a high RTO.
For important legal or financial data, a company is going to want to achieve near-zero RPO and a reasonable RTO so that business activities can be resumed. When looking at data shares which are primarily used as cache, or scratch disks, such as for rendering or video production work, the data stored on there is trivial, while service availability may heavily impact productivity.

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