Many batch joba are run at night. This is usually to free up system resources for the users who primarily work during the day. Batch jobs may also be run during the day.
Many online processes are run using CICS. There is also TSO/ISPF, ROSCOE, IMS, and others that are online.
One big difference between batch and online is that online is run connected to a terminal while batch is run detached from a terminal.
Hope this helps,