What are the main functions of AWX (and of the Automation Controller built on it)?

A web UI to run and watch playbooks, role-based access control, job scheduling and workflows, a REST API for integration, Git synchronisation of playbooks, and container-native execution on Kubernetes.

Plain Ansible is a command-line tool: one person runs ansible-playbook from a terminal. That stops scaling once a team shares automation. AWX adds the layer a team needs around it:

• Web UI: start playbooks, browse inventories and follow job runs and their output centrally, instead of in someone's terminal history.
• RBAC (role-based access control): fine-grained rights per team and user, often connected to LDAP, so a helpdesk member may run "restart web service" against production without getting the SSH keys.
• Job scheduling and workflows: run automation on a timer, and chain jobs into workflows with conditional steps and approval steps ("only deploy after a person clicks approve").
• REST API: lets monitoring or ITSM (IT service management) tools trigger jobs, for example a ticket system that starts a remediation playbook.
• Version-control integration: playbooks are synchronised straight from Git repositories such as GitHub or GitLab, so what runs is what was reviewed.
• Architecture: runs container-native on Kubernetes, as a single node or in a high-availability topology.

Go deeper:

• Ansible AWX documentation — the user guide covers projects, inventories, credentials, job templates and workflows.
• ansible/awx on GitHub — source, release notes and the AWX Operator for Kubernetes.