Creating a Checkmk user gives an operator access to the monitoring site. A local account can sign in to the web interface, receive notifications, and see the hosts and services allowed by its role and contact-group membership.
Checkmk separates permissions from responsibility. Roles such as Administrator, Normal monitoring user, and Guest user decide which actions the account may perform, while contact groups decide which hosts and services the user can see and receive notifications for.
Use Normal user login with password for a person who signs in through the web interface. Use an automation user or automation secret only when scripts or API clients need credentials, and keep at least one administrator account with normal login access before changing machine-account settings.

The username is the login name. Use Full name for the display name that may change later.
Notification delivery also requires responsible contact-group membership and a notification rule that sends to those contacts.
Related: How to create a Checkmk notification rule
By default, Checkmk requires at least 12 characters for local user passwords unless the site policy has been changed under Global settings → User management.
Roles grant permissions. If several roles are assigned, Checkmk grants the combined permissions from those roles.
Select Everything only when the account should be responsible for every host and service assigned to the predefined all contact group.
User and responsibility changes that appear in the pending bundle are not part of the monitoring environment until activation completes.
Related: How to activate Checkmk pending changes
Use Setup → Events → Test notifications without sending a real message first, then check Predicted notifications for the new user.
Related: How to test Checkmk notification rules