Lightning Web Component is the new way of building Lightning Components in Salesforce. There are high chances that you may end up with some common error.
UNDERSTAND GETTER IN LIGHTNING WEB COMPONENT
OPEN LIGHTNING COMPONENT FROM URL BUTTON IN LIGHTNING
When name attribute is defined in slot element, it is known as named slots where as slot without a name attribute is called unnamed slots.
You might have passed data from Parent Lightning web Component to Child Lightning Web Component but have you ever came across any requirement to pass markup from Parent to child in Lightning Web Component?
Lightning Web Component has the ability to pass data from parent component to child component, but sometime you might need value change handler in child Lightning Web Component when the value is passed from parent Lightning Web Component.