Caching helps in improving performance of an application by maintaining easily accessible copy of the data. Aspnet Core comes with two easy to use and testing friendly caching abstractions.
Memory Cache will store data in to local server's memory caching.
Distributed Cache will hold the data cache in a centralized location which is accessible by servers in cluster. It comes with three implementations out of the box : In Memory (for unit testing and local dev), Redis and Sql Server.