Releases let you version and release flow changes. To create a release, click the Release button in the top right of the flow editor screen.
Then, add notes and select the version of the flow you will release on pop-up window. There are 2 types of releases you can perform, i.e. Create release and Create and promote. Create release is used to publish the flow only in Test environment, while Create and promote will make the flow go live both in Test and Production environment. By default, the flow you release will be live in Test only. However, if you want to promote the flow to Production, click the ▼ button and select Create and promote.
After creating a release, you can check if the release is active from the release management screen.