As you know there many oracle process are running as background process.

You may now some of them or you may not. So You can find related process from oracle documentation or you can follow below steps:

Some of Oracle Process:

oracle@veridata$ ps -ef | grep ora_
oracle 3116 1 0 10:33 ? 00:00:28 ora_pmon_orcl
oracle 3118 1 0 10:33 ? 00:00:49 ora_psp0_orcl
oracle 3120 1 15 10:33 ? 00:39:48 ora_vktm_orcl
oracle 3124 1 0 10:33 ? 00:00:19 ora_gen0_orcl
oracle 3126 1 0 10:33 ? 00:00:21 ora_diag_orcl
oracle 3128 1 0 10:33 ? 00:00:19 ora_dbrm_orcl
oracle 3130 1 0 10:33 ? 00:01:14 ora_dia0_orcl
oracle 3132 1 0 10:33 ? 00:00:18 ora_mman_orcl
oracle 3134 1 0 10:33 ? 00:00:22 ora_dbw0_orcl
oracle 3136 1 0 10:33 ? 00:00:27 ora_lgwr_orcl
oracle 3138 1 0 10:33 ? 00:00:47 ora_ckpt_orcl
oracle 3140 1 0 10:33 ? 00:00:12 ora_smon_orcl
oracle 3142 1 0 10:33 ? 00:00:09 ora_reco_orcl
oracle 3144 1 0 10:33 ? 00:00:45 ora_mmon_orcl
oracle 3146 1 0 10:33 ? 00:01:20 ora_mmnl_orcl
oracle 3154 1 0 15:34 ? 00:00:10 ora_qmnc_orcl

As you can see there are many process is running on my system.

Those process’s details available at

SQL> select NAME,DESCRIPTION from v$bgprocess order by 1;

NAME       DESCRIPTION
ABMR Auto BMR Background Process
ACFS ACFS CSS
ACMS Atomic Controlfile to Memory Server
ARB0 ASM Rebalance 0
ARB1 ASM Rebalance 1
.
.
ARB5 ASM Rebalance 5
ARB6 ASM Rebalance 6
ARB7 ASM Rebalance 7
ARB8 ASM Rebalance 8
ARB9 ASM Rebalance 9
ARBA ASM Rebalance 10
ARC0 Archival Process 0
ARC1 Archival Process 1
ARC2 Archival Process 2
ARC3 Archival Process 3
.
.
NSV0 Data Guard Broker NetSlave Process 0
NSV1 Data Guard Broker NetSlave Process 1
NSV2 Data Guard Broker NetSlave Process 2
NSV3 Data Guard Broker NetSlave Process 3
NSV4 Data Guard Broker NetSlave Process 4
NSV5 Data Guard Broker NetSlave Process 5
and so on
Hope It Helps