Here you have an example in which we are instantiating a child component called childComponent: The ending tag is compulsory, you cannot omit it.This change has been done to follow web standards.

This means that if the component name is something like m圜amelCaseName, the reference in markup will be my-camel-case-name. You just need to reference the child component in the markup of the parent component. Lightning Web Components can be composed in a similar way to Aura components. To talk about communication, we first need to talk about composition. The communication patterns are different from Aura, and are one of the culprits of Lightning Web Components superb performance. One of the keys to learn how Lightning Web Components work is to understand how components can communicate between each other.

If you don’t know what it is about, check this post I published some time ago. Lightning Web Components is the new programming model that Salesforce released early this year.