Full Page Cache(FPC) is the feature of Magento that significantly speeds up page load time, reduces the load on the server, improves website ranking and remarkably increases sales conversion.
The power of full page caching lies in its ability to store the full page output in the cache. This decreases the server load for when consequent pages are loading. If your Magento 2 website had a high traffic, full page caching is almost compulsory as it keeps the server load low and avoid downtime at times of high traffic. As the server needs are reduced by getting all rendering pages from the cache, the performance of your website improves as a result.