A big part of becoming a MariaDB expert is learning how to effectively and efficiently use the command-line mysql client program. Often we will interact with MariaDB using custom programs that have been developed for specific needs. At a lower level though, every interaction that these programs have with MariaDB can be done with the command-line client.
MariaDB has a client-server architecture, which means there are two parts to it—the server, which is the part that does the heavy, behind-the-scenes stuff, and a client, which is the part that we use to access and interact with the server. We hardly ever interact directly with the server part. There are many different clients for MariaDB, but only one is maintained by the MariaDB developers and included with every copy of MariaDB—the mysql command-line client.