After I create an Oracle database it provides extensive tables inside it with strange names. What exactly are these tables? Must I have them? Otherwise, how do i avoid creating them?

Fundamental essentials table names:

LOGMNR_UID$ LOGMNR_SESSION_EVOLVE$ LOGMNR_GLOBAL$ LOGMNR_RESTART_CKPT_TXINFO$ LOGMNR_AGE_SPILL$ LOGMNR_SPILL$ LOGMNRC_DBNAME_UID_MAP LOGMNR_LOG$ LOGMNR_ERROR$ LOGMNR_PROCESSED_LOG$ LOGMNR_FILTER$ LOGMNR_RESTART_CKPT$ LOGMNR_GT_TAB_INCLUDE$ LOGMNR_GT_USER_INCLUDE$ LOGMNRT_MDDL$ OL$ OL$HINTS OL$NODES LOGMNR_DICTSTATE$ LOGMNRC_GTLO LOGMNRC_GTCS LOGMNRC_GSII LOGMNR_SEED$ LOGMNR_DICTIONARY$ LOGMNR_OBJ$ LOGMNR_TAB$ LOGMNR_COL$ LOGMNR_ATTRCOL$ LOGMNR_TS$ LOGMNR_IND$ LOGMNR_USER$ LOGMNR_TABPART$ LOGMNR_TABSUBPART$ LOGMNR_TABCOMPART$ LOGMNR_TYPE$ LOGMNR_COLTYPE$ LOGMNR_ATTRIBUTE$ LOGMNR_LOB$ LOGMNR_CDEF$ LOGMNR_CCOL$ LOGMNR_ICOL$ LOGMNR_LOBFRAG$ LOGMNR_INDPART$ LOGMNR_INDSUBPART$ LOGMNR_INDCOMPART$ LOGMNR_LOGMNR_BUILDLOG LOGMNR_NTAB$ LOGMNR_OPQTYPE$ LOGMNR_SUBCOLTYPE$ LOGMNR_KOPM$ LOGMNR_PROPS$ LOGMNR_ENC$ LOGMNR_REFCON$ LOGMNR_PARTOBJ$ LOGMNRP_CTAS_PART_MAP LOGSTDBY$APPLY_PROGRESS MVIEW$_ADV_OWB DEF$_AQERROR DEF$_AQCALL MVIEW$_ADV_PARTITION MVIEW$_ADV_INDEX HELP SQLPLUS_PRODUCT_PROFILE LOGSTDBY$HISTORY LOGSTDBY$SKIP_SUPPORT LOGSTDBY$SKIP LOGSTDBY$SKIP_TRANSACTION LOGSTDBY$PLSQL LOGSTDBY$FLASHBACK_SCN LOGSTDBY$SCN LOGSTDBY$APPLY_MILESTONE LOGSTDBY$Occasions LOGSTDBY$PARAMETERS REPCAT$_SITES_NEW REPCAT$_EXTENSION REPCAT$_INSTANTIATION_DDL REPCAT$_EXCEPTIONS REPCAT$_TEMPLATE_TARGETS REPCAT$_RUNTIME_PARMS REPCAT$_SITE_OBJECTS REPCAT$_TEMPLATE_SITES REPCAT$_USER_PARM_VALUES REPCAT$_OBJECT_PARMS REPCAT$_TEMPLATE_PARMS REPCAT$_TEMPLATE_OBJECTS REPCAT$_TEMPLATE_REFGROUPS REPCAT$_OBJECT_TYPES REPCAT$_USER_AUTHORIZATIONS REPCAT$_REFRESH_TEMPLATES REPCAT$_TEMPLATE_TYPES REPCAT$_TEMPLATE_STATUS REPCAT$_FLAVOR_OBJECTS REPCAT$_AUDIT_COLUMN REPCAT$_AUDIT_ATTRIBUTE REPCAT$_PARAMETER_COLUMN REPCAT$_RESOL_STATS_CONTROL REPCAT$_RESOLUTION_STATISTICS REPCAT$_RESOLUTION REPCAT$_RESOLUTION_METHOD REPCAT$_CONFLICT REPCAT$_Arranged_COLUMN REPCAT$_COLUMN_GROUP REPCAT$_PRIORITY REPCAT$_PRIORITY_GROUP REPCAT$_REPGROUP_PRIVS REPCAT$_DDL REPCAT$_REPCATLOG REPCAT$_REPPROP REPCAT$_Produced REPCAT$_KEY_Posts REPCAT$_REPCOLUMN REPCAT$_REPOBJECT REPCAT$_SNAPGROUP REPCAT$_REPSCHEMA REPCAT$_Tastes REPCAT$_REPCAT DEF$_Pressed_TRANSACTIONS DEF$_ORIGIN DEF$_PROPAGATOR DEF$_TEMP$LOB DEF$_LOB DEF$_DEFAULTDEST DEF$_CALLDEST DEF$_DESTINATION DEF$_ERROR AQ$_INTERNET_AGENT_PRIVS AQ$_INTERNET_AGENTS AQ$_Agendas AQ$_QUEUES AQ$_QUEUE_TABLES MVIEW$_ADV_PLAN MVIEW$_ADV_JOURNAL MVIEW$_ADV_INFO MVIEW$_ADV_PARAMETERS MVIEW$_ADV_EXCEPTIONS MVIEW$_ADV_OUTPUT MVIEW$_ADV_Qualified MVIEW$_ADV_CLIQUE MVIEW$_ADV_GC MVIEW$_ADV_FJG MVIEW$_ADV_AJG MVIEW$_ADV_ROLLUP MVIEW$_ADV_LEVEL MVIEW$_ADV_FILTERINSTANCE MVIEW$_ADV_LOG MVIEW$_ADV_FILTER MVIEW$_ADV_TEMP MVIEW$_ADV_PRETTY MVIEW$_ADV_SQLDEPEND MVIEW$_ADV_BASETABLE MVIEW$_ADV_WORKLOAD LOGMNR_SESSION$ LOGMNR_PARAMETER$

Thanks.

The tables you've listed connect with Oracle's LogMiner utility, Materialized Views and Advanced Replication amongst other things. You need to leave these alone.

It's known as the information dictionary, where Oracle stores info on its modules and tables. Begin to see the Oracle documentation.

Should you choose custom installation, you might choose not to install modules. Which provides you less modules, along with a more compact data dictionary.