Yes, the Cisco DNA license is required for cat9k switches. Cisco DNA is the platform that can automagically configure your network as well as monitor it closely to make sure it's behaving as you expect. To give you just a couple of popular features:
1) Software Image Management finally makes Cisco device upgrades seamless. It does all the best practice health checks before and after the device upgrades so that you can upgrade multiple devices simultaneously with confidence. Also Cisco DNA can tell you which Security Advisories are impacting your network.
2) Network Assurance collects all the standard syslog, netflow, and snmp data it can get its hands on and lets you go back in time to see what was happening to a specific host or network device at a specific point in time in the past. That makes troubleshooting network issues significanly easier for a variety of problems.
You can start with these and manage your network as you do today, but eventually you'll be interested in taking advantage of the time savings Cisco DNA provides in deploying new devices from scratch. It probably will make your life easier to be able to unpack a switch from a box, plug it in and have it automatically configured for you.
Depending on how you like to research to learn more, I recommend reviewing youtube videos of various features (I like them because they are short), Cisco Live presentations (long and thorough), and the following FAQ.
https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/digital-network-architecture/nb-06-digital-nw-architect-faq-cte-en.html
