Automated backups are performed daily and have a retention period ( of max 35 days) and can be used to restore and create a new database.
Manual (on-demand) backups are called Snapshots and have no retention period ( they do not expire and must be deleted manually). They backup entire DB instance, not just individual DBs and can cause suspension of I/O in case of single AZ (from few seconds to few minutes).
In case of multi-AZ there is not hiccup (with the exception of SQLServer) because backup is taken from the StandyBy instance.
Snapshots can be exported out of RDS to S3 and allow further analysis with other tools like Athena, SageMaker or EMR.
You can choose to simply export specific databases, tables or schemas.