SID is word or DB_UNIQUE_NAME that precedes the DB_DOMAIN. For example, the SID database, as seen in in the full global database name of bookstore.company.com.
SERVICE_NAMES, on the other hand, represent the names by which database instances can be connected to. A SERVICE_NAME will follow the format of the SID followed by the database domain, like so: DB_UNIQUE_NAME.DB_DOMAIN
TNS Names and Configuration
When connecting to an Oracle database, typically your database server will have tnsnames.ora, which is a configuration file that informs the server about NET_SERVICE_NAMES which are valid database connections. By default, this file is located at ORACLE_HOME/network/admin.
For example, a NET_SERVICE_NAME descriptor in tnsnames.ora may be formatted like this:
And listener.ora file, should be look it this.