Installation of DB2 Linux, Unix, Window (LUW) contains server and client tools. That means DB2 LUW can act as server and also as a client.
Every database connection on DB2 registered on catalog. Database has parent node catalog. So catalogues are tree view looks like. Local databases are automatically registered in database catalog.
To connect to remote database server we need to make catalog for the remote connection. After remote catalog has been registered, remote server will appear as local.