You would like multiple people to use your subscription
In free accounts, only one user/device can be monitored. In paid accounts you may monitor multiple users and devices depending on your subscription.
You should be aware, however that subscriptions for the home should be limited only to your own home, otherwise you may be giving up your right to privacy to a third-party.
In certain cases, where multiple people live in one household (such as a family), where multiple users (e.g. spouse or partner) may wish to be able to monitor the dashboards, you can allow multiple users to login with their own email addresses to view the data.
You can also create and delete ad-hoc accounts on the system, such as if you need a housekeeper to respond to potential attacks against a smart home whilst you are away on holiday.
You should never share your own password with anyone.