A microsite is an individual web page or a small group of pages with a single purpose or subject.
Small and local businesses usually have microsites as their primary websites. Bigger, more marketing-intense companies create many microsites besides their main website. They do that, so there are no distractions and links that can lead people away.
You can use microsites to promote different parts of your business. For example, to sell a specific product, service, event, or run a particular campaign. They can be a powerful tool to drive traffic and generate conversions.
You can host microsites can on a different domain or subdomain.