Oracle RMAN Question:

Channel is a link that RMAN requires to link to target database. This link
is required when backup and recovery operations are performed and recorded.
This channel can be allocated manually or can be preconfigured by using
automatic channel allocation.
The number of allocated channels determines the maximum degree of
parallelism that is used during backup, restore or recovery. For example, if
you allocate 4 channels for a backup operation, 4 background processes for the
operation can run concurrently.
Parallelization of backup sets allocates multiple channels and assigns
files to specific channels. You can configure parallel backups by setting a
PARALLELISM option of the CONFIGURE command to a value greater than 1 or by
manually allocating multiple channels.
RMAN> CONFIGURE DEVICE TYPE PARALLELISM 2 BACKUP TYPE TO COMPRESSED
BACKUPSET;