Metadata is lower-level information. It is very important for web pages and is used by search engines. Examples of metadata are Title- title, Description- brief description, Keywords- keywords.
Microsite is a small website that serves as a support for the main website. It can contain extended information about a specific product or, for example, competitions.
Merchandising is a marketing tool that is mainly used in the retail industry. It focuses on the correct placement of goods, but also on their prices and availability in the store or e-shop. In the online world and e-shops, merchandesign partially replaces UX, which is dedicated to making the purchase as pleasant as possible for the e-shop visitor.